88 L. A. BORRADAILE. 



which there is but one perforation — that for the sternal artery (11, fig. 20). On each side 

 of the ganglion arise, at wide intervals, three stout nerves for the first three legs. In 

 front and behind, the longitudinal commissures join it as two more slender strands, one 

 close on each side of the middle line but quite distinct. Behind the nerve for the third 

 leg of each side, between it and the longitudinal commissures, the small nerves for the 

 fourth and fifth legs arise. In this region there are also several very fine, thread-like 

 nerves arising from the dorsal surface of the ganglion and running backwards. 



In front of the nerve for the first leg, between it and the circumoesophageal com- 

 missures, half-a-dozen nerves for the mouth parts arise (9, fig. 20). These come off, not 

 as in the thoracic ganglion of Pagurus figured by Bouvier, at one level, along the edge of 

 the ganglion, but at different points scattered over its surface in that region. Two, in fact, 

 arise quite on the dorsal surface. Here again there are several small nerve-threads inter- 

 mingled with the stouter nerves leaving the ganglion. The nerves of the two sides are 

 not absolutely symmetrical but the asymmetry is not very marked. 



The abdominal chain. Leaving the thoracic ganglion the longitudinal commissures run 

 backwards as far as the beginning of the sixth abdominal segment. During the whole of 

 their course they remain distinct save where, in each segment, a ganglionic swelling binds 

 them together. Nerves are given off, not only from the ganglia, but also from the inter- 

 mediate portions of the commissures. The nerves of the two sides are not strictly sym- 

 metrical. 



The brain and circumoesophageal commissures are easily exposed by removing the stomach 

 from above, when they are found lying respectively against the anterior and ventral body-wall. 

 The hinder part of the circumoesophageal commissures, with the thoracic ganglion and the 

 nerves leaving it, is protected by a stout endosternal skeleton of the macrurous type, joined 

 by the usual rib-like bars with the endopleurae and epimera, which form the rest of the 

 internal skeleton. The abdominal chain lies along the ventral side of the abdomen under the 

 muscle-band. 



vii. The generative organs (PL III. fig. K, a — c). 



A. 77(6 male organs. The testes lie imbedded in the dorsal part of the liver and 

 more or less completely hidden by the lobes of that organ. They are not symmetrical, 

 the right being placed farther back than the left. It is also rather the larger of the two. 

 Each consists of a much coiled, sacculated tube compacted into a firm, elongate mass, en- 

 larged at the hind end. From this enlarged part arises the vas deferens, a somewhat 

 complicated structure, divided into three regions — (1) the conducting tube, (2) the spiral, 

 (3) the glandular tube. The conducting tube is a short, irregularly twisted duct arising 

 from the inner, ventral aspect of the testis at its hinder end. In calibre it is smaller 

 than the glandular tube, but rather larger than the spiral. This latter is a fine, semi- 

 transparent pipe arranged in one close coil of about thirty turns. The glandular tube is 

 stout, of an opaque white colour, and thrown into many irregular loops. It runs forward 

 along the inner side of the testis, becoming less convoluted as it goes, traverses the 

 anterior part of the abdomen, and finally passes almost insensibly into the ductus ejacula- 

 torius — a simple, uncoiled tube, slightly wider than the vas deferens. 



