SEA-FISHERIES LABORATORY. 341 



vessels. It appears to be the case that the efferent portion 

 of the oviduct opens before each spawning, and closes again 

 by adhesion of its walls when the act of spawning is over. 



The external oviducal opening leads into a short 

 chamber (OdJ) into which both right and left ovaries open. 

 Od." is the cavity of the right organ. The septum in the 

 figure is the fused internal walls of both ovaries. All this 

 terminal chamber in the ripe fish is filled up with ova 

 which have dehisced from the ovigerous lamellae. On the 

 internal walls of the ovary are the ovigerous lamellae, 

 longitudinal folds of the wall in which the ova are 

 developed. Text-fig. 3 represents part of a transverse 

 section of the ovarian wall in a spent fish and shews a 

 single ovigerous lamella. In this condition the wall is 

 thick. Externally there is a loose connective tissue layer, 

 and in the thickness of this a thin sheet of black pigment. 

 Internal to this layer is an investment of unstriated 

 muscle fibres of some thickness in the spent ovary, but 

 very thin in the ripe condition. Within this, and filling 

 up the thickness of the lamella, is a somewhat dense con- 

 nective tissue stroma. The surface of the lamella is 

 formed by an epithelium which in places has a rather 

 obscure structure, but here and there contains patches of 

 small rounded cells, obviously a germinal epithelium. 

 From this the ova proliferate into the thickness of the 

 lamella, and come to lie freely in the stroma, at first near 

 the surface of the former. Many such ova of different 

 sizes are represented in the section. The largest have a 

 distinct zona radiata, the nucleus is large with a distinct 

 nuclear membrane and with diffused chromatin. An 

 obvious ring of large spherical nucleoli is seen in contact 

 with the nuclear membrane. Often the nucleus is con- 

 tracted away from the membrane, leaving a clear space. 



The Male organs. — The testes are undivided flattened 



