ZOOLOGY AND BOTANY, MI0KO80OPY, ETC. 889 



applied in a ttick layer on the internal wall of the cell. Afterwards, 

 the rings disappear, and a large-meshed network of small microsomes 

 is produced grouped together under the form of filaments, and sur- 

 rounded by other microsomes, placed at a greater distance from one 

 another. Finally the microsomes aggregate, principally on the 

 internal face of the cylindrical wall, into masses sharply defined by a 

 membranous layer of protoplasm, and separated by large ellipsoidal 

 vacuoles. In these masses the microsomes are grouped in ovoid or 

 fusiform corpuscles, provided with two cilia. 



Thus are formed, in one and the same cell, a great number of 

 gpermatozoids, which at first move slowly, and subsequently with 

 extreme rapidity, especially in the vicinity of the large vacuoles; 

 after a few minutes they escape from the cell by an opening 

 originating in the wall, and penetrate by a similar opening into one 

 of the neighbouring cells, filled with oospheres, there to accomplish 

 fecundation. This process of the formation of spermatozoids does 

 not take place simultaneously, but successively in the different proto- 

 plasmic masses separated by vacuoles of one and the same cell. Of 

 a cell-nucleus nothing is visible. 



4th. The plants of Splioeroplea annuUna are susceptible of being 

 notably modified in their structure and their mode of reproduction 

 according to circumstances. The vigorous specimens are monoecious, 

 the weak dioecious. Some were found which consisted only of one 

 cell or a small number of cells, and which produced only oospheres or 

 only spermatozoids. When fecundation is not effected, the oospherea 

 also appear capable of developing by parthenogenesis, that is, by 

 fission and formation of zoospores in the mother-cell. 



Zoochorella.* — G. Kessler describes a fresh example of symbiosis 

 between a rhizopod and an alga, viz. Zoochorella living within a 

 heliozoon, Acanthocystis chcetophora. He succeeded also in obtaining it 

 from Hydra; and in addition, within Amceba radiosa, he observed 

 diatoms as well as other parasitic and larger algae. 



Volvox Globator. Is it a Hollow Sphere ? j — J- I^evick maintains 

 that whilst the idea of Volvox being hollow has passed as so self- 

 evident as scarcely to have been challenged, " it is easy for micro- 

 scopical students to demonstrate for themselves the certainty that 

 those charming little globes are not hollow but solid." 



"As frequently happens, little accidents lead to the discovery of 

 facts which might otherwise seem out of one's reach ; and a few years 

 ago, when I made frequent collections of this organism, I gathered 

 some containing the rotifer which is said to make Volvox its nest, 

 Notommata parasita of Ehrenberg; and while watching these little 

 fellows in the home of their adoption, was surprised to see that 

 they were eating something of sufficiently solid consistency to keep 

 them in position in a part of the Volvox where, according to the 

 hollow sphere theory, there should be nothing to eat, or to bear 



* Arch. Anat. u. Phys., 1882, pp. 490-2 (1 pi.). See Bot. Centralbl., xv. 

 (1883) p. 257. 



t Rep. and Trans. Birm. Nat. Hist, and Micr. Soc. for 1882, pp. xxiii.-v. 

 Ser. 2.— Vol. III. 3 



