MOEPHOLOGY OF CYCLOPS. 35 



budded off from the subhypodermal connective tissue on each side the rectum, in the 

 Nauplius of the second stage (with rudimentary maxillae). 



The Female Organs. 



The ovary (PL II. fig. l,ov.) appears, at first sight, as a nucleated syncytium at its 

 hinder end ; hut treatment as aforesaid with oil of cloves for dissection determines 

 enough shrinkage to prove that each nucleus has its proper investment of protoplasm. 

 While in Cyclops I have been unable to trace the formation of the ova, a dissection of 

 Calanas has shown me karyokinetic figures, and evident multiplication of nuclei at the 

 hinder free end of the ovary, and there only. The latter statement certainly holds good 

 for Cyclops. Towards the middle of the gland a clear space appears round the 

 reticulated nucleus, the " germinal vesicle," which becomes larger. The body of the 

 ovum becomes filled with spheroidal food-yolk granules, and the ova increase in size as 

 they pass into the oviduct. The oviducts (PI. II. figs. 1, 6, od.) seem to be outgrowths 

 from the ovary; even in young examples with an incomplete number of joints (eleven) to the 

 antennules and three segments to the abdomen, they may be traced to the place where the 

 vulva is seen afterwards to open ; but in one with only two abdominal segments I failed 

 to trace it down to the fifth thoracic nerve. At this stage it has already begun giving 

 off those uterine processes (Pis. II. fig. 1, & III. fig. 5, u.) so conspicuous a little later by 

 the dark colour the ova which fill them assume. The uterine processes are as follows : — 

 A pair, each of which bifurcates, runs forward to the head ; a second runs back next the 

 dorsal median line to the second or third thoracic segment ; these are given off from the 

 oviduct near its origin. Besides these, the oviduct itself, full of ova, first bends down 

 obliquely back and then passes parallel to the latter pair, between the great extensors 

 and flexors, and internal to the motors of the oar-feet, to the fourth segment, giving off a 

 short blind ventral uterine process in eacli intersegmental space; beyond the fourth seg- 

 ment it contains no ova, and forms an elongated dilatation in the sixth segment before the 

 vulva. Owing to the dark colour of the ova, the body of the pregnant female is elegantly 

 banded. The wall of the oviduct seems composed of a fibrillated coat, in which I have 

 sought in vain for a distinct arrangement of muscles ; it is lined by very short granular 

 nucleated cells with a look of hypoblast. Its uterine part doubtless secretes food-yolk, 

 while its lower part, as first shown by Grube, is filled with a cement-substance (forming 

 a stained coagulum in prepared specimens), which sets in water. Often, by opening 

 the fresh animal, the masses of ova become surrounded by a membrane, which can only 

 proceed from this cement, so that possibly the uterine parts also secrete it. Each 

 vulva is a transverse lateral slit behind the genital valve ; it receives on its inner side the 

 short sperm-duct (PL II. fig. 6, sp.d.) from the spermatheca. 



The spermatheca (PL II. figs. 1, 6; PI. III. fig. 1, spth.) is a sac in the dilated ventral 

 side of the sixth thoracic segment, and extending into the first abdominal segment 

 anchylosed with it. It is superficial to the trunk-muscles (flexors). It forms a double 

 bag, its two lobes being anterior and posterior, nearly equal, transversely oval, and united 

 by a short isthmus ; into the base of the upper lobe leads upwards and forwards a short 



