152 DK9CEIPTI0N OF [^Poli/gastrica. 



is proceeding, and the young are increasing in size, the siirrotmding 

 induvium, which is a distinct lorica, is observed to expand in a cor- 

 responding degree, but continues entire until its numerous occupants 

 have come to maturity, when it is seen to biu'st, and set them at 

 liberty. The animalcules thus set free multiply in the same manner, 

 and also by means of ova — in which case the expansive property of 

 the lorica comes equally into operation. 



All the genera (excepting, perhaps, Gyges), are provided with 

 organs of locomotion, which consist, as with the Monads and Crypto- 

 monads, of a single or double flagelliform very delicate proboscis ; and 

 hence it is that, when they are in clusters, the entire group appears to 

 be ciliated, or beset with hairs. Transparent digestive cells are visible 

 in the Volvox glohator and Gonitim pectorale, but in most of the species 

 the green ova liide them from our sight. The propagative apparatus 

 is evident in all the genera, with the exception of the JJroglena, under 

 the form of ova grains, one or two round glands, and a contractile 

 bladder. 



The family is disposed into ten genera : five are fui'nished with 

 the visual organ, situated at the anterior part of the body, and five 

 are without it. In the former, a sensitive system is consequently 

 presumed. 



The following is an analysis of the family : — 



f r vibrating j g 



f I proboscis absent ( .» & • 



Lorica box-like< 



•s < 



- . . , I vibratiner 



^ Lonca 8»ngle<; | ^^„,,„^,,i« nrp 



absent 



^^jj ^ i.unca ».ugie^ L proboscis present 



j clusters tabulated or in plates Gonium. 



Lorica double Sj-ncrypta. 



Tail present Synura, 



C f tail present tJroglena. 



Self-division both 



equal and perfect < ( proboscis single Eudorina. 



(no internal globes) tail absent. . \ 



{_ \ proboscis double Cblamidomonas, 



„,,,... , r proboscis single Spheerosira, 



Self-division unequal I ' ° 



(forming internal < 



globes) I proboscis double Volvox. 



There is a tendency in recent observers to refer many, or even all 

 of the Volvocina to the vegetable kingdom. Tor instance, Dr. Car- 

 penter says, " It is not by any means certain that the Volvocina are 



P4 



