310 OVARY AND INTRA-OVARIAN EGG IN TELEOSTEANS. ■ 



It is to be noticed, however, that the thickened masses occur 

 round the inner surface of the membrane only at intervals, and that 

 the modified inner portion becomes decidedly thin at the other parts. 

 One of the thickened masses is seen in fig. 12, the total thickness 

 in this case being '25 mm. Following the progress of the masses, 

 we find that the cells thus added to the stroma continue for some 

 time to keep together, and that those on the inner margin continue 

 to divide rapidly, extending inwards amongst the loosely arranged ova. 

 They often give off chains of cells which follow separate directions, 

 twine round ova, and extend until they eventually reach the 

 germinal epithelium. We find, in short, that the whole supporting 

 structure of the ovary has been laid down. 



These chains of cells then begin to flatten, they stain more and 

 more deeply, the nuclei become less distinct, and the appearance 

 becomes once more that of ordinary fibrous connective tissue. 



The spaces between the fasciculi of fibrous tissue are generally con- 

 sidered to contain albuminous matter, and therefore with the rupture 

 of these cells from the ovarian membrane an albuminous substance 

 would at the same time be given to the ovary. Such a substance 

 has been described as being present in the ovaries of Teleosts, its 

 function being considered to be that of a lubricant, useful in allow- 

 ing the eggs to be readily extruded at the spawning period. The 

 origin of this substance may be explained in this way. 



In treating on the great ova in the common dab I have stated 

 that the quite unripe condition persists all through the autumn and 

 winter months, that the ovary is then in a resting or inactive con- 

 dition. 



I am not prepared to consider this statement as applicable to all 

 Teleosts, because in some cases, if a resting period does occur, it 

 must be a short one. I am not even prepared to say that all Pleuro- 

 nectids have a distinct resting period, because the reproductive 

 organs of this genus, as of others, show a considerable diversity of 

 arrangement, and the spawning periods are often widely apart. 

 Still the condition seems also to obtain in round fishes, since I find 

 it in the hake. A circumstance which may affect the condition 

 very decidedly is the extent of time taken by any one species in 

 getting rid of all its spawn. If the intervals between the expulsion 

 of successive batches of ova are prolonged, then it follows that the 

 anterior part of the ovary is very much later in getting into its 

 resting condition, and that by the time it has done so a progressive 

 change may have already set in at the periphery of the posterior or 

 early part of the organ. 



The Plaice, for instance, has a spawning period which extends 

 over a very considerable length of time, and it also sheds a large 



