NORTH SEA INVESTIGATIONS. 369 



Now if we examine a spent female of the same group the con- 

 ditions are very different. In the first place^ the anterior or free 

 region of the ovary is enlarged and flaccid ; a distinct depression 

 can be felt from the outside on either side of the haemal spines, 

 extending well-nigh to the caudal peduncle. On removing the 

 muscular wall in this region we find the posterior process of the 

 ovary much elongated, thin, and flaccid, and very loosely lodged 

 between the spines and the muscles ; whilst in the anterior region 

 the connective tissue which formerly united the muscular and 

 skeletal elements ventral to the front of the ovary may have to a 

 great extent disappeared, so that a mesentery forms in this region 

 the only boundary between what one may term the alimentary and 

 reproductive portions of the visceral cavity. The length of the 

 ovary is variable, but is seldom if ever less than half of that between 

 the first hsemal spine and the caudal peduncle. 



On opening the ovary the contents are found to vary according 

 to the time which has elapsed since spawning. If the latter is 

 recently over, the germinal epithelium shows traces of ruptured 

 follicles, and more or fewer ripe and decomposing ova are to be met 

 with ; at this stage their nature will be at once obvious. In spent 

 fish at any period which I know the lumen of the ovary is wide, 

 and the germinal epithelium of the posterior process is arranged in 

 conspicuous longitudinal ridges. It may contain, as in all plaice 

 which I have examined, a number of small ''active" ova, in addition 

 to a host of ''inactive" ones, but I am uncertain whether these 

 represent the early condition of next season^s crop, or only ova 

 which, though they pass the inactive stage, are absorbed without ever 

 reaching a considerable size. It appears most probable that after 

 spawning the ovary continues for some time to produce a certain 

 number of active ova, which, however, are successively absorbed, with- 

 out ripenmg, until the approach of the next season. Otherwise it is 

 necessary to suppose that an ovum in this species, and others which 

 in this respect agree with it, takes the best part of a year to ripen 

 after it has passed the " inactive " condition. 



The dab is so far the only form in which I have found only inactive 

 ova in the germinal epithelium of spent ovaries. 



Of a number of females examined in August the ovaries of most 

 exhibited the features which I have just described as characteristic 

 of spent fish, but in three the characteristics were those of immature 

 fish. There was no difference whatever in the ova in the ger- 

 minal epithelium, but on instituting a careful search certain whitish 

 gelatinous bodies were met with in the ovary ducts of some of the 

 larger fish. These proved to be the remnants of ripe ova, the zona 

 being the most recognisable feature. There could be no doubt that 



