294 ROCHESTER ACADF.MV OF SCIKNCE. [Juilt; 25, 



protoplasm of the cell thrust out through openings in the cell-wall, 

 with which they lash the water, thereby propelling their colonial 

 globe. Each cell is the center of six other cells with which it is con- 

 nected by the retaining net-work just mentioned, which not only 

 serves the purpose of binding the whole colony together, but the 

 further and more important purpose of putting each individual in 

 communication with every other individual in the colony. 



There is, without doubt, a free circulation of water through the 

 globe at all times, thus supplying food and o.xygen to both parent 

 and offspring. 



Dr. Carpenter, in speaking of these gonidia, says : " It is impos- 

 sible not to recognize the precise similarity between the structure of 

 this body and that of the motile encysted cell of Protococcus pluvialis. 

 'I'here is, in fact, no perceptible difference between them, save that 

 which arises from the regular aggregation of the cells in Volvox, which 

 normally are detached in Protococcus.'" Professor \Villiams says : "A 

 singular provision is made in the structure of the gonidia, consisting 

 of a slender elastic filament, by which each is attached to the cell- 

 wall. At times it is seen to thrust itself out as if in search of food, 

 it is then seen quickly to recover its former position by means of the 

 contractility of the elastic filament." 



Another interesting fact not generally noted in regard to Volvox, 

 first pointed out by Mr. Buck, of the Royal Society, is that "at certain 

 times, under favorable conditions, individual members of the colony 

 detach themselves and lead an independent life ; but it is noted that 

 when this is the case the gonidia are double, hence the colony is not 

 ruptured by the departure of the individual." Again, Dr. Hicks 

 says : "Under favorable conditions the contents of the cell may be 

 converted into a free moving mass of naked protoplasm, a veritable 

 Aniivba to all appearances, and as such it will vacate its cell and go 

 roaming about in the cavity of the Voliox" The intent and destiny 

 of these last forms is not known. 



Professor Cohn is to be credited with the honor of having done 

 much toward working out the generative processes of Volvox, which 

 are as follows : Any one or more of the gonidia may increase in 

 size, when it is seen to be composed of a number of somewhat angu- 

 lar green masses, separated by the interposition of a somewhat trans- 

 parent substance, the whole being inclosed in a transparent envelope 

 of considerable thickness. This, the young Volvox, increasing in size, 

 soon appears like a button attached to the inner surface of the parent 



