120 



POLYOECHIS PENICILLATA. 



ing with each other (Fig. 179) ; this gives to these Medusae a very 

 peculiar appearance, differing entirely from any other family of Hy- 

 droids, and for which 1 would propose the name of Polyorchidse. The 

 polar axis is the longest ; the spherosome has its greatest 

 width at the level of the ovaries (Fig. 179) ; from this 

 point it turns rapidly towards the abactinal pole, while it 

 scarcely tapers towards the actinostome, giving the sphero- 

 some the appearance of a cylinder with a rounded top ; 

 the thickness of the spherosome is very uniform, projecting 

 but slightly in the inner cavity of the bell (Fig. 181), at 

 the point of attachment of the digestive cavity ; the diges- 

 tive cavity is long, slender, and exceedingly movable, terminating in 

 foiu- lobes (Fig. 182), and extending to the opening of the veil; there 

 are four genital organs of unequal length, attached at the highest point 

 (Fig. 180) of the four chymiferous tubes, hanging freely in the cavity 

 of the bell ; they are arranged one behind the other, along the upper 

 extremity of the chymiferous tubes, the longest equallmg half the 

 height of the inner bell. The diverticula from the main tubes com- 

 mence immediately at the base of the ovaries, where they are quite 

 small ; they gradually increase in size for about half the length of the 

 chymiferous tubes, whence they continue nearly of the same size to the 



circular tube ; the ofishoots are somewhat more numei'ous in the lower 

 part of the tube. (Fig. 179.) The tentacles are very contractile (com- 

 pare Figs. 183 and 179) ; when drawn up, they are scarcely half the 

 length of the spherosome ; they project horizontally from the chymif- 

 erous tubes for a short distance, and from the point where a conical 

 dark-purple ocellus is placed are then bent at right angles to their 

 former direction ; it is only the lower part of the tentacle which is 

 capable of expansion ; when the tentacles are fully expanded, they 

 extend three or four times the length of the bell. The genital sacs, 

 the chymiferous tubes, the tentacles, and the digestive cavity, are of a 



Fig. 181. Section of the bell. 



Fig. 182. Part of the disk of Fig. 179, seen from the abactinal pole. 



Fig. 183. Two of the marginal tentacles in a contracted state. 



