138 Transactions of the Society. 



Oogenesis of the Mollusc Patella. 



Patella is the common sea-limpet ; a study of the oogenesis of 

 this mollusc shows that the formation of the yolk is a more com- 

 plicated process than is the case with another mollusc such as 

 Helix (the snail) or Limna^a. Just as in Helix the youngest 

 oocytes contain a typical Golgi apparatus formed of discrete rods 

 (dictyosomes) and a group of mitochondria. While in Helix the 

 Golgi apparatus spreads out through the egg cytoplasm, and 

 becomes an important contributor to the number of formed bodies 

 of the Qgg, the Golgi apparatus in Patella is from the first begin- 

 ning of deutoplasmagenesis a much more important part of the 

 two protoplasmic inclusions (mitochondria and Golgi apparatus)". 

 Kot only do the Golgi elements surpass tlie mitochondria in their 

 growth activities, but many of them become associated in some 

 way with the yolk spheres. This is to say, that however the yolk 

 spheres may be formed, be it from the mitochondria, archoplasm, 

 or simply in the ground cytoplasm, the Golgi elements later become 

 stuck upon the surface of many, if not all, of the yolk spheres, and 

 form a most important part of the yolk substance. 



The important point to note is that in two molluscs. Helix and 

 Patella, the Golgi apparatus in each case differ a good deal in the 

 extent in which they take direct part in the formation of true yolk 

 bodies. We believe that in the case of Patella the Golgi apparatus 

 provides most of the yolk spheres of the full-grown egg, but in 

 Limmea either the mitochondria (or the ground cytoplasm) are 

 most active in this respect. 



In PI. II, figs. 6 and 7, we have given figures representing the 

 staining changes which come over the Golgi element (stained with 

 OSO4) or the mitochondrium (stained in acid fuchsin after chrome- 

 osmium fixation) during their metamorphosis into yolk bodies. 



Oogenesis in Amphibia and Insecta. 



In some ways the oogenesis of Amphibia typified by Rana or 

 Triton (Molge), and of Insecta by Apanteles and Dytiscns, presents 

 the same general features. The mitochondria increase in number 

 and tend to form a filamentous mass on the peripheral part of the 

 growing oocyte. When deutoplasmagenesis begins the yolk discs 

 appear at the periphery of the egg, in the mitochondria, but though 

 the mitochondria may lie towards the centre of the oocyte, or 

 entirely spread throughout the oocyte, the yolk discs appear at the 

 periphery. We have observed this also in the oocyte of the 

 sparrow {Passer domesticus). 



Note. — (1) The yolk discs of insects and amphibians appear at 

 the periphery of the Qgg where mitochondria happen to lie ; and 



