NICOTHOE ASTACI. 429 



apparatus of Nicothoe is the peristaltic action of its parietes, which is 

 continued even after its removal from the body, and which here is evi- 

 dently in relation with the " phlebenterism" exhibited in the arrange- 

 ment of the digestive system. No proper respiratory organs exist in 

 these simply-organized beings ; the diffusion of the blood through the 

 interior of the body, subservient alike to respiration and nutrition, 

 seems to be entirely effected by the contractions of the intestinal 

 walls; and the proper chylific viscera themselves perform the duties 

 of the lacteal, circulatory, and respiratory apparatus of the higher 

 animals. 



(1108.) As is the case with the generality of the Lerneans, the male 

 of the Nicothoe was, until recently, unknown to naturalists a circum- 

 stance attributable to two causes: in the first place, the individuals 

 of the male sex are very diminutive in all the genera belonging to this 

 group, insomuch that from their size they seem rather like parasites on 

 the female ; and secondly, because in some of them, which have been 

 more particularly studied, a phenomenon is observable analogous with 

 what occurs in the Aphides among insects there occur whole genera- 

 tions of fertile females, and most probably, also, gemmiparous (nursing) 

 races, during a certain portion of the year, as is the case with Limnadia* 

 and Daphnia-^ ( 1072). 



(1109.) The male of Nicothoe is represented in fig. 223, 2, magnified 

 in the same proportion as the female. The generative apparatus of the 

 female is largely developed : it is situated principally in the lateral ap- 

 pendages of the body, of which it occupies a considerable part, being 

 lodged by the side of the digestive caeca. The ovarium (fig. 223, 1, h) is 

 very irregular in its shape ; anteriorly it is bifurcate, and its whole 

 surface has a sacculated appearance. The oviducts (i) become conjoined 

 near the mesial line, and then bend downwards to terminate at the 

 vulva. These canals are frequently filled with ova throughout their 

 whole length. From the oviducts the eggs pass directly into the enor- 

 mous ovisacs (/), suspended from each side of the caudal portion of the 

 body, between the lateral appendages, in which they are contained until 

 sufficiently mature for exclusion, when the ovisac, bursting, gives issue 

 to hundreds of minute Mcothoes hatched in its interior. 



(1110.) On emerging from its prison this little creature is exceedingly 

 active, and presents exactly the form of a Cyclops (fig. 223, 3) ; neither 

 would any one ever suspect it to be the same creature which vegetates 

 upon the branchiae of the Lobster. However, no sooner has it fixed 

 itself in that situation than its body begins to swell out laterally, in the 

 shape of two tubercles that sprout from the sides of the body just 

 behind the third thoracic segment, into which the viscera are seen to 

 penetrate ; and as these tubercles enlarge, the animal becomes gradually 



* Fide Ad. Brongniart, " M&n. sur le Limnadia," M<m. du Mus. 1820. 

 f Straus-Durckheim, " M6m. sur le Daphnia," Mem. du Mus. 1820. 



