300 



PROCEEDINGS OP THE NATIONAL MUSEUM. 



VOL. 89. 



coelom at the top and sides and in front of the stomach is completely 

 filled, the processes almost touching one another and those along 

 either side of the mid-line approaching till they come in actual con- 

 tact (fig. 23). 



The first lateral process is the longest, while the last one given off 

 is usually the thickest. These gravid processes not only fill all the 

 available space in the coelom, but their growth arches the dorsal sur- 

 face of the carapace until it is strongly curved (fig. 24); indeed, it 

 goes so far as to become practically spherical in TJiersitina. 



At the same time they push back the posterior margin of the cara- 

 pace until it overlaps the second and sometimes part of the third 

 thorax segments, giving the fully mature female very much the 



appearance of a tadpole, except of course 

 for the egg-strings. 



Cement glands. — Unlike the free cope- 

 pods, in which, according to Claus, Gruber, 

 and Hertog, the cement or ''Kittsubstanz" 

 is contained in the posterior portion of the 

 oviduct, Ergasilus possesses a pair of cement 

 glands similar to those of the Caligidae. 

 These are situated in the posterior por- 

 tion of the thorax on either side. Each 

 consists of a long and narrow tube some- 

 what curved, the one facing the other like 

 two parentheses marks, and each lying be- 

 low the oviduct on its side (fig. 21). The 

 tube is cylindrical, tapers somewhat anteri- 

 orly and posteriorly, and shows faint lines 

 or grooves dividing it transversely into 

 about a dozen segments (fig. 25). Its con- 

 tents are colorless and structureless, but 

 stain deeply with eosin in sections. At its 

 posterior end it narrows abruptly into a short duct, which opens 

 into the oviduct close to the vulva. These shell or cement glands 

 are difficult to discern in the livnig copepod, but preservation in 

 weak formalin often brings them out quite clearly. On examining a 

 section of one of these glands under a high power, it is seen (fig. 25, 6) 

 that the wall is composed of a single layer of culumnar cells, whose 

 nuclei are situated near the inner ends. These cells increase in length 

 from the proximal toward the distal end of the gland. 



There is a second increase at about the center of the gland, where 

 the cells from opposite sides approach each other until only a narrow 

 neck-like lumen is left between their inner ends. This probably 

 represents the mouth of the really glandular portion of the organ, 

 the remaining proximal portion being more of a duct. The entire 



Fig. 20.— The second ltterine proc- 

 esses FORMING ANTERIORLY IN 

 THE head; POSTERIORLY CAN BE 

 SEEN THE OVIDUCTS CONNECTED 

 WITH THE FIRST UTERINE PROC- 

 ESSES. 



