122 



ut development (tig. 53, 0' .) can be seen attached to the 

 wall, but gradually projecting more and more as they 

 increase in size until they are set free in the cavity 

 (fig. 53, 0.). 



The ova are large cells about O'Uo mm. in size, and 

 when lying in the alveoli are polyhedral in shape. The 

 )iucleus is very large, spherical or oval in shape, and about 

 two-thirds the diameter oi the cell. A delicate network 

 is present, extending over the nucleus, and in addition, 

 they are small granules staining with eosin, and a 

 conspicuous nucleolus. This is situated close to the 

 periphery at one side of the nucleus. In some cells more 

 than one nucleolus is present, there being often a large 

 and two smaller ones at its sides. 



The cytoplasm is granular and dense, and around the 

 ovum is a prominent vitelline membrane Avhich leaves an 

 opening — the micropyle, at the point where the egg 

 remained last attached to the epithelium of the alveolus. 



The spermatozoa (fig. 53, S.) are rather small and of 

 the typical shape ; in fixed preparations the head is oval 

 in shape and stains very intensely. From the middle of 

 the broad end a long flagellum arises. In the alveolus 

 the tails of the spermatozoa are generally all directed in 

 the same way towards a point in the centre or nearer one 

 end where the duct opens, whilst the heads are directed 

 towards the wall of the alveolus. Both spermatozoa and 

 ova travel along the same gonoducts to the exterior. 



EMBRYOLOGY. 



I have been unable to obtain enough specimens of 

 P. maximus sufhciently ripe at the same time to artificially 

 fertilise the eggs, but hope to continue this work 

 at some future date. It has been already pointed out 



