214 M. E. Claparede on Actinophrys Sol. 



may glance at tlie part it plays in the oeconomy of the animal. 

 Ehreuberg^s hypothesis of a seminal vesicle emptying itself 

 regularly every minute, or even more frequently in most Infu- 

 soria, is quite indefensible. There remain, therefore, only two 

 different views as to the nature of the contractile vesicles, — they 

 are either true hearts, like those possessed by most animals fur- 

 nished with blood-vessels, or heart-like organs allied to the 

 Poliau vesicles of the Echiuodermata, or to the pulsating dilata- 

 tions of the aquiferous vessels of the Cestode and Trematode 

 worms, and of the Rotifera. 0. Schmidt has maintained the 

 latter view, and the great similarity of the contractile vesicles of 

 the Infusoria and Rotifera is certainly in its favour. Never- 

 theless we cannot adopt this opinion, as these contractile vesicles 

 are deficient in the leading characteristics of an aquifei'ous sy- 

 stem, namely the existence of ciliary movement in its smaller 

 branches, and especially of an immediate connexion with the 

 surrounding medium. We cannot indeed deny the existence of 

 the former of these characters, as no vessels have hitherto been 

 discovered amongst the Infusoria, but the other indispensable 

 condition is certainly wanting. It might be supposed that the 

 openings of the aquiferous system, if present, had escaped us 

 from their small size, but such a supposition is rendered ex- 

 ceedingly improbable by the position of the contractile vesicle in 

 Actinophrys. If an opening existed at that point, it must be 

 visible, or at all events currents would be observed in the w'ater 

 during the reception and expulsion of fluid. As this is not the 

 case, the contractile vesicles of the Infusoria can only be com- 

 pared with the heart-like organs of the sanguiferous systems of 

 other animals. 



Ehronberg can never have seen the animal feeding, otherwise 

 he would have recognized the true destination of the so-called 

 proboscis, for the reception of food certainly takes place at 

 quite another part of the body. Stein has also, as already 

 stated, mentioned the contractile vesicle of Actinojjhrys, but he 

 rejects Siebold's explanation, merely because "he is acquainted 

 with no infusorial animal in v.hich the contractile space can be 

 protruded externally." He recurs therefore to an opinion not 

 far removed from Ehrenberg's, and endeavours to explain the 

 reception of food by the action of this organ. Thus, according 

 to Stein, the prey \vhen captured by the tentacles is brought in 

 contact with one of the protruded vesicles, to which it adheres ; 

 this then suddenly disappears into the cortical layer, drawing 

 the prey with it, which at first lies in a funnel-shaped pit formed 

 by the contraction of the vesicle, but is afterwards drawn into the 

 interior of the cortical layer by the rolling over of the margins 

 of the pit, and thence passes to the medullary layer. Stein con- 



