ONE OF OUR COMMON MONADS.

BY PROF. ALBERT H. TUTTLE.

SINCE the investigations of Clark, Carter and others upon the sponges and their allies, anything which adds to our knowledge of the Flagellate Infusoria is of especial interest. I have fortunately had an opportunity of making a careful study of a genus Urella of Ehrenberg, about which thus far but little that is satisfactory has been known.

Until recently but little has been known of the real nature of the Monadina. As a natural consequence, organisms have been referred to the different genera of this family upon very slight

Fig. 88.

A colony of about forty Monads.

study and superficial resemblances. Urella, which Ehrenberg describes thus, "aggregate monads, free-swimming, tailless, devoid of an eyespeck and having one or (doubtfully) two flagelliform filaments," has of course received its share of attention until one might think from the "species" and the

figures given that the diagnosis of the genus had been "anything very minute, aggregated, free-swimming," whether Infusorian or Alga making no difference.

When, therefore, I found in a collection made at Spy Pond, near Cambridge, on the 25th of November last, a large number of individuals of this genus (probably the species glauconia Ehr.), I made use of the opportunity for a careful study of it, devoting my spare time to it daily as long as I continued to find it in the water; what follows is therefore the result of a number of observations, at which each point has been examined and verified.

* Communicated to the Section of Microscopy of the Boston Society of Natural History, Dec. 13th, 1871.

Urella probably finds its nearest ally in Anthophysa, differing from that genus principally in being free-swimming instead of fixed upon a stalk. The number of monads in a colony is quite variable, almost every number having been seen, up to forty or fifty; in this, however, as in many other respects, the constant activity of the colonies renders it impossible to speak with absolute certainty; even when cornered so that they could no longer progress in the direction in which they had been moving, they continued to revolve upon their axes with considerable rapidity, making it impossible to count them with accuracy. Occasionally, a group of five or six or even two or three and not unfrequently a

Fig. 89.

An ideal section through a colony of Monads.

single monad would be seen, and these were more available for purposes of study, though the larger groups were more frequent. From such measurements as I was able to make while they were in motion, I should say that the average length of each monad was about one two-thousandth and the breadth one five-thousandth of an inch; but these dimensions varied a good deal with the size of the colonies, the individuals in the larger groups being more elongated and narrower than those in the smaller ones. The form may be described as conical with a rounded base not at right angles with the axis of the cone, the part at the greatest distance from the apex being the one nearest the apex of the colony; in colonies of over ten or twelve the axis of the cone being also bent towards the apex of the group, especially in those monads near the base. The form of the larger colonies varied from hemispher

ical to raspberry or even mulberry shape, the form shown in Fig. 88 being the most common.

I was unable to find any trace of a common investing membrane in either the larger or the smaller groups, nor do I believe that any such membrane exists in any true species of Urella.

I was able to distinguish clearly two flagella, both arising from a point near the most elevated side of the base of the cone. The Fig. 90.

A group of five Monads.

larger one was stiff, arcuate with the concave side toward the base before mentioned, somewhat longer than the body of the monad, and very plainly seen with any objective above a quarter-inch; the smaller is very delicate, short and incessantly active. I first

saw it with a Wales' fifteenth, but after becoming familiar with its appearance I was always able to detect it with a Tolles' eighth or a Hartnack number nine.

Fig. 91.

I am not certain as to the number of contractile vesicles but it is my opinion that there is but one: sometimes a larger number of clear spaces would be seen in the body, but they were not observed to contract. I do not wish, however, to speak with any degree of positiveness upon this point, as I was not able to keep a single monad in view long enough to satisfy myself, on account of the constant revolution of the colonies. As regards the ingestion of food I have seen

Two Monads.

• something, though not as much as I could wish, as this is still a disputed question. I fed them with indigo which they ate readily, and I frequently watched its ingestion. On account of their incessant motion, I was not able to satisfy myself of the existence of a definite mouth, but I did not see a single instance of the indigo being received at any point except very near the com

mon base of the flagello, and in every instance observed, the act of ingestion was preceded by a quick bending of the larger flagellum by which the particle of indigo was thrown against the surface of the body in a manner similar to that described by Professor Clark in his observations upon Monas. So far as I was able to follow the process, whenever a colony reduced its rate of motion sufficiently to permit of careful observation upon this point, it was so much like the process described in Monas as to leave little doubt in my mind that it was substantially the same: although as I have said I did not see a distinct mouth.

Fig. 92.

A Single

It appears probable, now that the Monadina are better understood, that we shall soon be able to recognize in them a well-defined family of the Flagellate Infusoria, although doubtless many forms that have been assigned Monad. to that group are vegetable in their nature; these will be gradually removed and those forms which are unquestionably animal will be distinguished: among these it seems to me the genus Urella as described by Ehrenberg will undoubtedly take its place.

Figure 88 represents a colony of about forty monads; Fig. 89 an ideal section through such a colony; Fig. 90 represents a group of five; Fig. 91 of two, and Fig. 92 a single monad. I have attempted to sketch in this last the position of the large flagellum when throwing a particle of food against the mouth region. All the above figures are enlarged one thousand diameters.

REVIEWS AND BOOK NOTICES.

GEOLOGICAL SURVEY OF OHIO.*-Though this is but a yearly report of progress, yet it is an important contribution to American geology, both in its purely scientific and practical aspects. We are convinced that when the final reports shall be published, the citizens of the State of Ohio will feel proud of the thorough and able manner in which the survey has been carried on and com

Report of Progress in 1870. By J. S. Newberry, Chief Geologist. Including Reports by E. B. Andrews, Edward Orton, J. H. Klippart, Assistant Geologists; T. G. Wormley, Chemist; G. K. Gilbert, M. C. Read, W. B. Potter and Henry Newton, Local Assistants. 8vo, pp. 568, with maps and engravings.

pleted, and of the monument to scientific zeal and learning erected in the series of magnificent works which we are promised in the present report. We make a few extracts regarding the discoveries made by the survey. The fossil invertebrates are to be worked up by Profs. Hall and Worthen, many novelties having been found.

"The interesting collection of Amphibian remains, which includes more than a dozen species, obtained by myself some years ago from the coal rocks of Ohio, has been placed in the hands of Prof. E. D. Cope, of Philadelphia. He has described them and caused them to be carefully drawn. They supply material for six or more plates, which will add much to the interest of our final report.

The illus

The fossil fishes and fossil plants found in the State have been described by myself. They have been drawn by Mr. T. Y. Gardner and Mr. G. K. Gilbert in a style that has not been surpassed in this country, and some of their work is equal to any of a similar character done by the best European draughtsmen. trations already prepared of this material form over forty plates; and I do not hesitate to say that the objects which they represent are not exceeded in scientific interest by any that have been described by palæontologists. The fossil fishes comprise many genera and species, some of which are more remarkable for their size, their formidable armament or peculiarities of structure than any of those which formed the themes of Hugh Miller's glowing descriptions. These have, for the most part, been found only in Ohio; have never been described and will not fail to deeply interest all the intelligent portion of our population.

In my first report of progress (p. 5) I have shown how useful, even indispensable, fossils are to the student of geology, and I am happy to know that their significance and value are coming to be generally appreciated. There are, however, yet some intelligent men, even editors and members of the legislature, who cherish the notion that there is nothing which has any value in this world but that thing which has a dollar in it, and that so plainly visible as to be seen by them. Such men, to quote the language of one of them, 'don't care a row of pins for your clams and salamanders, but want something practical.' Happily the class to which they belong is rapidly passing away. Were it otherwise I should endeavor to prove to them that the fossils which they despise are eminently practical; that they are labels written by the Creator on all the fossiliferous rocks, and that no one can be a geologist who has not learned their language."

We are promised that the final reports will consist of four volumes, of which the first two will be on Geology and Palæontology with a geological map on a large scale, vol. 3 on Economic Geology and vol. 4 on Agriculture, Botany and Zoology.