82 



Female or<jans. 



In the three species represented by female colonies it is probably not too much to say 

 that all the adult zooids without exception possess a pair of ovaries. These make their 

 appearance at an early stage in the budding, so that it is really only the very young buds 

 ill which gonads cannot be detected. 



The ovaries are a pair of organs, symmetrically disposed on either side of the middle 

 line, and they occur in the dorsal ])art of the third ])()d\-cavity, between the anus and the 

 pharyn.\. The major part of the organ is composed of an ovoid mass containing the eggs. In 

 adult specimens it is usual to find that in addition to a number of immature eggs the ovary- 

 contains a single egg in which a large tjuantity of yolk has made its appearance. The ripe 

 ovarian egg thus reaches a large size (as much as 380 ij.. in length in C. gracilis)^ and in an 

 individual which contains a ripe egg there is commonly some asymmetry of the two ovaries, 

 one of which may be much smaller than the other owing to the fact that it contains no ripe 

 egg. In favourable specimens, there is an indication of a central cavity in the ovary; and 

 the organ appears to be a hollow sac, the lining epithelium of which gives rise to the eggs. 

 The ripe egg occupies the ventral part of tlie ovary (fig. 42), while the remains of the 

 germinal epithelium are at the base of the oviduct. 



The oviducts are one of the most characteristic features of Ccphalodiscus. Their wall 

 contains a pigment which is not dissolved by spirit, and the oviducts are thus so readily 

 seen through the thin body-wall that they were originally described as eyes. The oviduct is a 

 tubular prolongation of the cavity of the ovary. The external apertures are situated on the 

 dorsal swelling of the metasomc which immediately .succeeds the central nervous system. 



The frontal sections of C. Icvinseni represented on Plate X will serve to explain the 

 relations of the ovaries and their external apertures. On reaching the posterior end of the 

 collar (fig. I 1 8) the dorsal projection of the metasome first makes its appearance as a 

 longitudinal ridge of body-wall attached to the dorsal side of the collar. The two collar-cavities 

 are here separated from one another by the dorsal diverticulum of the pharynx (div.), and 

 between this and the central nervous system is seen the extreme tip of the right third hoch- 

 cavity [p. cj^). The longitudinal ridge of body-wall separates from one another the entrances to 

 two deep recesses lined by the epidermis of the metasome, and bounded in front liy the part 

 of the collar-wall which contains the lateral nerve-tract passing from the central nervous system 

 to the stalk. This is shewn, on the left side, in fig. 119, while in fig. 120 it will be seen that 

 the same oviduct opens into the posterior .side of this recess. On the right side of fig. i 20 the 

 recess is already passed, and the oviduct is no longer connected with the body-wall. The part of 

 the body which contains the oviducts is marked by a conspicuous dorsal furrow (figs. 119 — 122). 

 Each oviduct is supported by a lateral or ovarian mesentery, which reaches the body-wall 

 dorsally (figs. 119, 120), while more ventrally it leaves the body-wall and passes along the 

 dorsal mesentery of the metasome to the dorsal vessel. In the region of the external opening 

 of the oviduct the ovarian me.sentery passes from llie Ixuly-wall, near the middle line, to the 

 oviduct in such a way as to appear to cut off a posterior section of the third body-cavity 

 (figs. 119, 120); but in later sections in which the oviduct has relincjuished its connexion with 



