300 



ZOOLOGY. 



The arrangement of the ventral system of arteries is very 

 peculiar and quite characteristic of this animal. The o?so- 

 phageal nervous ring, and in fact the entire nervous cord, is 

 ensheathed in a vascular coat, so that the nervous system 

 and its branches are bathed by arterial blood. The veins 

 are better developed than usual ; there being in the cephalo- 

 thorax two large collective veins along each side of the in- 

 testine. 



Closely connected with the two large collective veins are 

 two large brick-red glandular bodies each with four branches 

 extending up into the dorsal side of the cephalo-thorax. 

 They are probably renal in their nature. 



Both the ovaries and testes are voluminous glands, each 

 opening by two papillas on the under side of the first ab- 

 dominal feet. At the time of spawning the ovary is greatly 

 .distended, the branches filled with green eggs. 



Unlike most Crustacea, the female king-crab buries her 

 -eggs in the sand between tide-marks, and there leaves them 

 at the mercy of the waves, until the young hatch. The eggs 

 are laid in the Northern States between the end of May and 



rh- 



FIG. 266. 



FIG. 267 



Fig. 266. Embryo of King-crab, enlarged ; am, serous membrane ; c/t, chorion. 

 Fig. 267. The same, more advanced. 



early in July, and the young are from a mouth to six weeks 

 in hatching. 



After fertilization the yolk undergoes total segmentation, 

 much as in spiders and the craw-fish. When the primitive 

 disk is formed the outer layer of blastodermic cells peels off 

 soon after the limbs begin to appear, and this constitutes 



