Microscopical Society. 3009 



diaphragm, the circular mouth of which is of about half the diameter of the cell above 

 it. Beneath this diaphragm, an elongated cavity or cell extends, and opens on the 

 outer surface of the sponge ; the whole length of the cell, from the inner edge of the 

 diaphragm to its termination near the outer surface, being closely studded with tessel- 

 lated nucleated cellular structure : within the diaphragm, and between the inner ter- 

 mination of the incurrent orifices, are situated the cilia, which are of excessive tenuity, 

 and comparatively of considerable length. Upon focussing the diaphragm, the cilia 

 may be seen in rapid motion within the area of the circular orifice, many of them 

 being tipped with a minute portion of gelatinous or of fecal matter ; and the whole 

 of them continually oscillate in a plane parallel to the edge of the diaphragm, occa- 

 sioning a continual current through its orifice. 



Although both the presence and action of the cilia were very clearly shown by this 

 mode of examination, still neither the extent of surface covered by them, nor their 

 insertion, could be determined. By dividing, however, one of these cells through its 

 whole length, which after many trials and failures was at last effected, portions of 

 these, examined in the same manner as in the preceding instances, exhibited ciliary 

 action ; and as the vital energy decreased and their motions became languid, one 

 cilium in particular was observed, which continued for nearly half an hour to wave 

 gently backward towards the outer surface of the sponge, and then rapidly forward to- 

 wards the mouth of the diaphragm. Many other cilia were observed, but none so 

 distinctly exhibited their peculiar action as this ; and it was found that although it 

 may be highly probable that the cilia are based upon, or spring from among, the tes- 

 sellated cells, it was not possible to ascertain the fact precisely ; but sufficient was 

 shown not only to prove the existence of ciliary action in the sponge, but also, by the 

 peculiar motion just described, to account for the flow of the currents in one direction. 

 —J. W. 



December 11, 1850. — Dr. Arthur Farre, President, in the chair. 



A paper by P. H. Gosse, Esq., ' On the Notomata parasita, Ehrenb., a Roti- 

 ferous Animal inhabiting the Spheres of Volvox globator,' was read. 



After stating that this animalcule was first described by Prof. Ehrenberg in 1835, 

 Mr. Gosse stated that he first observed it, June 26th, 1850, in specimens of Volvox 

 globator in water, given him by Alfred Rosling, Esq. He afterwards obtained it from 

 a little pool near the railway-station at Leamington, in Warwickshire. This creature 

 is too small to be seen by the unassisted eye, its greatest length being about T £ s th of an 

 inch. The author minutely described the anatomy of this animalcule, and also gave 

 an account of its curious habits, it being parasitic in the elegant Volvox globator, 

 within the globe of which it lives at ease, swimming about like a gold fish in a glass 

 vase. It appears to subsist upon either the green granules with which the gelatinous 

 surface of the Volvox is studded, or else upon the embryo clusters. It often happens 

 that two or more Notomata are seen in the same Volvox, and Mr. Gosse stated that in 

 one individual he had met with as many as four, with an egg besides. They are to be 

 found chiefly in the smaller Volvoces, and especially in those which have the embryos 

 in a very immature state. They have also been met with in the embryos themselves 

 when almost grown and nearly ready for escape from the parent globe. The operations 

 of this parasite do not appear to occasion any perceptible inconvenience to the con- 

 taining Volvox. In some spheres, eggs are found with Notomata ; in others eggs alone. 

 IX. F 



