OVARY AND OVAIiTAN OVA IN CERTAIN MAIJINP] FISHES. 101 



On the Histology of the Ovary and of the Ovarian 

 Ova in certain Marine Pishes. 



By 

 J. T. Ciiiiuiiigliaiii, M.A.Oxoo.^ 



With Plates 2—4. 



The Development of the Yolk. 



In my paper in the 'Journal of the Marine Biological 

 Association,' vol. iii, No. 2, p. 154, I have described the 

 development of the yolk in the plaice and dab as commencing 

 by the deposition of yolk granules in a thin layer near the 

 surface of the egg, and proceeding by the continual extension 

 of this layer towards the centre. I have also described and 

 figured the appearance of minute refringent globules dis- 

 tributed sparsely throughout the protoplasm of the egg, in 

 specimens of the sole which were examined a little time before 

 the commencement of the spawning season. Such globules 

 were also seen in spent ovaries of the sole, and seemed to 

 indicate that the formation of yolk occupied more than a year 

 in some fishes, while in the plaice and dab no sign of the 

 development of yolk was seen until some months after the 

 spawning season. 



I have since ascertained that among fishes with pelagic ova 



the one type of development is characteristic of eggs which 



have oil globules, the other of eggs that are not provided with 



such elements. Certain fishes, as for example the gurnards, 



have an extended spawning period, and ripen their eggs not 



* The researches described in this memoir were carried out. in the service 

 of the Marine Biological Association in 1895 and 189G. 



