36 PKOF. M. M. HAETOG ON THE 



median " vagina " from the copulatory pore (PI. II. fig. 6, spp.) lying at the boundary of 

 the thorax and abdomen. The sperm-ducts are short tubes, extremely difficult to make 

 out exactly in this species. I have, however, satisfied myself that they lead from the 

 posterior and outer part of the anterior lobe of the spermatheca. Each has a kink 

 pointing forward, which, as suggested by Grube, acts as a valve to prevent the exit of the 

 contents of tbe spermatheca. 



I have shown above that one muscle of the sixth appendage might raise the lower edge 

 of the vulva, rectify the kink of the sperm-duct, and effect the passage of the sperm to 

 the vulva. The spermatheca, like the ducts, have all a chitinous lining ; they are not 

 formed till the last moult ; they contain in the virgin female an irregular coagulum- 

 looking mass, in the fertilized female a mass of swollen polygonal spermatozoa. 



In oviposition the eggs, which have no vitelline membrane, and are polygonal by 

 mutual pressure in the body, pass out with the cement of the oviduct and spermatozoa. 

 The cement serves not only to attach the mass of eggs to the vulva, but by its coagu- 

 lation to give both a general investment to the eggs, chambered by partitions, and a 

 special investment to each egg. From 70-90 is a common number for the eggs in each 

 mass, which in this species has a real narrowly oval form, about 20 eggs long to 3 or 4 

 wide at the widest. The length of time for incubation varies chiefly, I believe, with the 

 temperature, for I never fail in getting a brood of Nauplii within 48 hours by keeping 

 a female bearing egg-sacs in a corked "Bolton's tube " half full of water in my waist- 

 coat pocket. 



The Hale Organs. 



The testis (PI. II. fig. 2, te.) resembles the ovary in form, position, and structure. 

 Its hinder end is a syncytium, containing rather large nuclei, some of which may be seen 

 dividing and showing karyokinetic figures (PL IV. fig. 13) : about the middle the nuclei 

 are well formed and large (male ova or spermatospores), in front they divide again, and 

 form the spermatozoa, apparently about 32 to each spermatospore, for 16 nuclei are 

 visible in a single view : I have not followed tlie full details of this process, which shows 

 even moderately well in only a few of my specimens. It is evident that other methods 

 must be resorted to than those given above for a full investigation on sperm agenesis, 

 and I would recommend tbe investigator to select a much larger and more transparent 

 form, such as the pelagic Calanus and Calanella, or perhaps even the Parasitica. 

 The paired vasa deferentia may be divided into four segments, which we may term 

 respectively vas efferens, epididymis, vas deferens (sensu restricto), and vesicula seminalis. 



The vas efferens (PL II. fig. 2, v.e.) is simply a short thin-walled tube running obliquely 

 down and back for a short distance from the anterior end of the testis. 



The next section or epididymis (PL II. fig. 2, ep.) forms a loop arched upwards and 

 inwards, the two limbs close together, and approaching one another on the median dorsal 

 line, the bight posterior, at about the middle of the third thoracic segment ; the lower 

 and inner limb continues the vas efferens ; while the upper outer limb at its end bends 

 down to form tbe vas deferens proper. The lumen of the epididymis is very small, but 



