C'HAS. \V. HARGITT. 



of various sizes, and those actually used ranged from about 5 to 

 ,}o cm. in length. No less care was exercised as to conditions 

 under which experiments were conducted. Three of the l.irge 

 aquaria supplied with running water were at my disposal during 



Fir,. 3 is a portion of one of the- large show-aquaria containing Protulu and 

 Spirographis. The varied aspect of the latter is quite marked, as will be seen by 

 comparing specimens in various positions. 



tin- period, and in addition l\vo special experimental a<|iiari.i of 

 smaller size, about 25 X 35 X 45 cm., also supplied with running 



