and on their Specific Differences. 5 



come to no other conclusion than that the two (laughters meet 

 after they have left their respective parents, when both the 

 spores and the spermatozoids having become ripe for fecunda- 

 tion, individuals forming the groups of the latter separate, burst 

 from their capsules into the cavity of the daughter, and from 

 thence find their way out into the water, and then into the 

 cavity of the daughter bearing the spore-cells, where they be- 

 come incorporated with the latter. 



Hence Volvox globator would appear to be dioecious, and not 

 monoecious as stated by Cohn ; and Sphcerosira Volvox not, strictly 

 speaking, another form of Volvox (/lobator, but the spermatic 

 form. Cohn, considering Volvox globator and Volvox stellatus 

 the same species, has taken his fecundating character from the 

 spermatic form of the latter, as will presently be seen. 



It is strange that, while I have often met with free sper- 

 matozoids in the cavity of the spore-bearing daughter of Volvox 

 stellatus, I have never been able to find any in that of Volvox 

 globator. I have, however, frequently seen colourless, fusi- 

 form, biciliated cells in the latter, each containing a large oil- 

 globule, which appeared to me to be the remains of the unem- 

 ployed spermatozoids, as they have only been present when the 

 spores had obtained their wavy, characteristic capsule and had 

 become of a deep-green colour (fig. 7 a), Again, the frequent 

 presence of Spij-illa in the daughters of Volvox globator bearing 

 impregnated spores, and their absence in those of Volvox stel^ 

 latus, indicate the existence of some aperture or apertures either 

 prepared for, or produced by, the entrance of the spermatozoids. 

 That such may exist without destroying the Volvox directly, is 

 shown by the fact that Rotatoria make their way into the latter 

 without causing them to perish. 



Volvox stellatus, Ehr. PI. I. fig. 3. 



Adult form. — Globular, slightly ovoid, consisting of three 

 generations or families within one another ; containing generally 

 eight daughters, in each of which there are generally eight 

 grand-daughters indistinctly visible. Daughters confined to the 

 posterior three-fourths of the spheroid, the anterior fourth being 

 empty. Progressing with the empty end forwards. Daughters 

 rotating (this marks the adult form here also) in their capsules 

 respectively, which are fixed to the internal periphery of the 

 parent. Grand-daughters small and indistinct, motionless, and 

 fixed to the internal periphery of the daughters respectively. 

 Peripheral cells conical and biciliated, not uniciliated as figured 

 by Ehrenberg. Size, 59-1880ths of an inch long and 54-1880tbs 

 broad. 



Development. — The daughter consists of an enlargement of 



