A STUDY IN MORPHOLOGY. 59 



somite (a) of an adult male, showing the first abdominal foot (PI. 1) and the basal 

 joints of the third maxilliped (J//>. 3), and the first, second, and third thoracic limbs 

 (Pi: 1, Pi: 2, Pr. 3). The testis (t) consists of a series of about eight pouches or 

 follicles, which hang down into the body cavity under the anterior end of the intestine 

 (/). The body of the animal is so thin that it is almost impossible to get a good 

 dorsal view without crushing the specimen; but a very careful examination of the side 

 view seems to show that there is only a single organ on the median line of the body, 

 as SEMPER states. On each side of the intestine, along the line where the testis joins 

 its wall, a small tubular vas deferens (vd) arises, and runs backwards along the side of 

 the intestine nearly to the end of the first abdominal somite, to which it seems to be 

 attached (at I) by a ligament. It then bends outwards and forwards upon itself to 

 form a second much larger portion (sp), which is parallel to and outside of the first 

 portion, and reaches nearly to the anterior edge of the first abdominal somite. The 

 third or terminal portion (sv) has a large cavity, thick walls, and it runs down to an 

 external opening which is situated on the outer edge of the sternal surface of the 

 thoracic region, behind the basal joint of the third pereiopod, and therefore in the 

 position which would be occupied by the basal joints of the fourth or fifth pereiopods 

 if they were present. 



There is a vas deferens, made up of these three portions, on each side of the body, 

 and the ventral nerve chain (ty) passes between their external openings. 



The more anterior follicles of the testis are almost perfectly transparent, but the 

 development of the male cells in the posterior ones gives to them a faint granulation. 

 The first division of the vas deferens (vd) has a small cavity, thin walls, and as it 

 usually seems to be entirely empty it is probable that the passage of the male cells 

 from the testis through it to the second division (sp) takes place quickly. The second 

 division (sp) has a very large cavity, and in it the male cells become arranged in a 

 single layer around the surface of a central core, which is formed of some dense 

 transparent adhesive substance. 



The sperraatophore appears to pass into the third chamber (sv) before it is completely 

 formed, as all those which were seen in the second chamber consisted only of a central 

 core and a layer of male cells, while those which were contained in the thick-walled 

 third chamber had an outer enveloping capsule. 



I found several specimens with a fully-developed spermatophore on one side of the 

 body and none on the other side, and was thus enabled to thoroughly satisfy myself 

 of the presence of two vasa deferentia, and two external openings. 



I was unable to discover how the spermatophore is transported to the body of the 

 female, or what part the clasping organ (c) upon the first pleopod of the male performs 

 during the act of copulation. 



Upon several occasions I observed a male clinging to the basal joints of the first 

 antennas of a female, but as I never succeeded in getting the pair under a lens with- 

 out separating them, I made no careful examination. Copulation usually takes place 



