320 



ZOOLOGY. 



The arrangement of the ventral system of arteries is very 

 peculiar and quite characteristic of this animal. The oeso- 

 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 yellowish 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 papillae 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 



FIG. 271. 



FIG. 272. 



Fig. 271. Embryo of King-crab, enlarged ; am, serous membrane ; cA, chorion. 

 Fig. 272. The same, more advanced. 



early in July, and the young are from a month 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 



