LAFCEA CALCARATA. 



125 



Fip. 191. 



wise the sterile Hydra reiuinds iis of a true Sertularian, with a few 

 thick tentacles, and a long digestive cavity, capable of great expansion. 

 The bell is attached to the stolon by a short stem, a mere bend in its 

 lower portion, so that the sterile individuals are set off a short distance 

 from the main stem. (Fig. 190.) The reproductive calycles are gigan- 

 tic, compared to the size of the sterile individuals. (Fig. lUO.) They 

 are few in number, not more than two or three to a stem, 

 and resemble those of L. amj^hoi'a ; only one or two Me- 

 dusa^ are developed simultaneously, the more advanced 

 one fdling the cavity of the capsule almost entirely. 

 (Figs. 190, 191.) The sterile individuals recall the Tubu- 

 larians, as do in fact all the Sertularians, in which the 

 connection between the bell of the sterile individuals and 

 the digestive cavity is not as intimate as in the true 

 Campanularians, giving us at the same time a measure 

 of the embryonic standing of the Tubularians, the Sertu- 

 larians, and the Campanularians ; the Medusas of this 

 Sertularian-like Hydromedusarium resemble more those 

 of the Tubularians than those of the Campanularians. The vertical 

 diameter of the Medusa is greater than the transverse ; the bell is of 

 moderate thickness, the abactinal part being slightly conical (Fig. 192) ; 

 the digestive cavity is short, and consists of four simple lobes, giving 

 the actinostome the shape of a cross. When it escapes from the repro- 

 ductive calycle, it has only two long tentacles, two slightly developed 



Fig. 192. 



Fip. 193. 



ones, and four more hardly perceptible in the middle of the space 

 between the four chymiferous tubes (Fig. 193) ; at the base of all the 

 tentacles, and over the whole surface of the digestive cavity, we find 

 large yellow cells scattered irregularly ; the long tentacles are highly 

 contractile ; a sj^iral of lasso cells, diminishing in size, and beginning at 

 a small distance from the sensitive bulb, winds round the tentacles ; 



Fig. 191. Uninjured reproductive calycle. 



Fig. 192. Medusa immediately after its escape from the reproductive calycle. 



Fig. 193. A Medusa somewhat more advanced, from the abaftinal pole. 



