96 NOTES AND MEMORANDA. 



publication of Mr. A. W. Bennett's valuable summary of Cobu's views 

 last year.* M. F. Henneguy, of tbe College of France, two years ago 

 communicated to tbe Academy of Sciences a note as to tbe reproduc- 

 tion of Volcox dioicus (Cobn), in wbich be pointed out tbe gradual 

 appearance of sexuality in tbese organisms, the male sex appearing 

 before tbe female in proportion as tbe species degenerates by sexual 

 reproduction. He bas now added further observations, of which the 

 following are the more important results.f 



The spores arising from the fecundation of the oospheres by tbe 

 antherozoids fall to tbe bottom of the water and remain in a stationary 

 state for a long time. Cobn thought that these spores must be dried 

 before germinating, though be did not observe tbe germination. 

 Cienkowski saw the contents of the spore divide, and be thought that 

 each sphere of segmentation became ultimately a ccEnobium. 



M. Henneguy has ascertained that, contrary to Cohn's opinion, the 

 spores of Volvox pass tbe winter in the water. Those observed were 

 collected in tbe miid of a basin of tbo Jardiu des Plantes, deep and 

 constantly filled with water. 



These spores, of an orange-yellow, possess two enveloping mem- 

 branes — an exospore with double outline, and a very thin endospore. 

 At the moment of germination, tbe exospore is torn open, and the 

 swollen endospore is seen to project through tbe openings. At tbe 

 same time tbe contents of the spore, separated from tbe endospore by 

 a clear space, divide into two equal parts, which, by successive 

 bipartitions, give birth to four, eight, sixteen, &c., small cells. Tbe 

 cells, at first orange-yellow, acquire a brown tint, becoming more and 

 more greenish in proportion as the work of division advances. When 

 tbe segmentation of the spore bas terminated, tbe cells form a 

 spherical layer analogous to tbe blastoderm of a boloblastic ovum. 

 Each element then acquires two vibratile cilia. The endospore dis- 

 appears and the young Volvox, thus constituted, moves freely in tbe 

 water. Tbe cells, at first very close together, separate one from 

 another by the interposition of a gelatinous matter. 



A fact interesting to note is the presence among the vegetative 

 cells of the Volvox still contained in the endospore, of elements larger 

 than tbe others, wbich will subsequently give origin to the daughter 

 colonies by a mode of division analogous to that observed in tbe spore. 



Tbe spores of Volvox therefore germinate in water, and each of 

 tbem produces a single colony by a jn-ocess of segmentation identical 

 with that which gives rise to a daughter colony at tbe expense of a 

 cell of tbe mother colony. 



Parasitism of a Coral on a Sponge.— Tbe discussion at tbe 

 January meeting on this subject will be found in tbe ' Proceedings ' 

 at p. 110. 



* See ' Pop. Sc. Keview,' N. S., vol. ii. p. 225. 



t 'Journal de Micrographie,' vol. ii. p. 485. 'Bull. Soc. Philomath. ,' Paris, 

 July, 1878. 



