466 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



not been detected. The nervous system is well developed, consisting of 

 a snpra-cesopbageal ganglion connected by commissures with a series of 

 four large ventral ganglions. The former lies immediately beneath the 

 oculiferous tubercle, to which it seuds large nerves; and from it are also 

 derived the nerves of the antennte, palpi, rostrum, and accessory legs 

 (Zenker). It seems probable, in view of the difterent origin of their 

 nerves, that the accessory legs are not, as often supposed, branches of 

 the first pair of ambulatory legs, but that they represent a pair of dis- 

 tinct appendages. Moreover, they are sometimes distinctly separated 

 from the first pair, which is notably the case in a peculiar genus from 

 Japan, apparently belonging to the genus Ascorhynchus Sars. 



The sexes are separate, and the reproductive organs extend far out 

 into the legs; their orifices are upon the lower side of the second joints 

 in all the legs. Eeference has already been made to the habit of carry- 

 lug the egg-masses, followed by the male. These egg-bearing forms 

 were long supposed to be females, but it has been conclusively shown 

 by Cavanna, and subsequently by Dohrn, that they are males. The 

 same faat was also noted in one or two species by Semper and Hoek. I 

 have been able to confirm this in nearly all of our species by examina- 

 tion of the contents of the reproductive organs. In the fourth joint of 

 each leg, in the male, is a large glandular organ, discharging by a num- 

 ber of openings arranged in an irregular row along the inferior side of 

 the joint. Dohrn surmises that the secretion of this organ serves as a 

 cement by which the eggs, when discharged by the female, are glued 

 into a ball and attached to the accessory legs of the male. 



Kroyer, Dohrn, and others have carefully studied the embryology. 

 The eggs are collected into round masses upon the accessory legs and 

 thus carried about by the male until after the escape of the embrj^os so 

 that his body is often covered with the curious young. Segmentation 

 of the yolk is complete. Prominences then appear/ upon the lower 

 side of the embryo, one of which ultimately becomes the rostrum, and 

 the others form three pairs of appendages, representing the future an- 

 tennae, palpi, and accessory legs. The condition of the larval antennse 

 has been already referred to. In most forms the embryo escapes from 

 the egg with only these three pah'S of appendages ; but a species of 

 Fallene, studied by Dohrn, passed through no metamori^hosis, leaving 

 the egg provided with the full number of appendages. 



The species of the genus PhoxicJdlidium are remarkable for passing 

 their early larval stages within the digestive cavities of certain tubula- 

 rian hydroids {RydracUnia, etc.), sis or eight of them sometimes living 

 together within a single polyi)ite. How they take up residence in the 

 body of their involuntary host has not been observed, but they have 

 been seen to escape by crawling out through the mouth. 



The Pycnogonida, as a whole, have never been very carefully studied 

 by systematic zoologists, though the observations of Dohrn, Quatrefages, 

 Zenker, and others have given us a tolerably full knowledge of their 



