QIJARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 415 



systematic position which must be assigned to this organism. 

 It seems to him that they are animals of large dimensions 

 belonging to the division of the Flagellata. 



A Hydroid Parasite from the Eggs of the Sterlet (Acipenser 

 ruthenus). — Professor Owsjannikoff, in the course of investi- 

 gations on the embryology of the Sterlet, came across a very 

 anomalous parasite living Avithin the thick egg-shell. He 

 figures it in the first part of the 17th volume of the ' Bul- 

 letin de I'Acad. Imp. des Sciences de St. Petersburg.' It is 

 not fixed, and lives for some time when liberated from the 

 egg in fresh water. It has somewhat the appearance of a 

 double or quadruple Hydra, there being generally four heads 

 of tentacles to each specimen sessile on a short conical body. 

 Each head has six tentacles. No thread-cells Avere detected. 

 The animal multiplies by transverse fission, an individual 

 with four heads splitting transversely into tAVO Avith tAVO 

 heads each of which in turn develop the complement of four. 

 The animal appeared to take in nourishment AA^hilst living 

 free in water containing confervoe, &c. The account now 

 given of this very strange organism is very incomplete, but 

 Prof. Owsjannikoff has no doubt that he Avill be able shortly 

 to give a more detailed notice of it. It is obviously a very 

 immature form. The mode of its entrance into the eggs is 

 altogether a paradox. 



Rotatoria. — At the meeting of Russian naturalists, held 

 this year at KicAv, Dr. Salensky described the development 

 of the summer eggs of Brachionus urceolaris. Tavo balls 

 result from the first cleavage, one of which then divides 

 further and surrounds the other. The enclosed mass then 

 divides. The trochal discs begin as an elevation surrounding 

 a depression of the outer cells, Avhich becomes the mouth. 

 The foot develops from the hinder part of this ridge. The 

 nerA^e ganglion develops from the outer layer of cells. The 

 inner cells give rise to the alimentary canal, to the lateral 

 glands, and (the author says) to the OA^ary. The rectum, like 

 the oesophagus is formed by a pushing in of the outer layer. 

 A middle layer of cells is said to arise (hoAv is not stated) 

 which give rise to the muscles. Salensky observes that the 

 formation of the trochal disc and of the foot takes place 

 exactly as does that of the velum and foot in the Mollusca, 

 as studied by him in the case of Calyptraea. 



Prof. Carl Semper describes (in ' Siebold's u. Kolliker's 

 Zeitschrift,' 3rd part, 1872) a remarkable spherical Rotifer, 

 Avhich he terms Trochosphcera cequatorialis. It occurs in 

 freshAvater ditches, in the rice-fields of Zamboanga, in the 

 Philippine Islands. 



