2 Transactions of the Society. 



batonettes surrounding the archoplasm (7). With the growth of 

 the egg, the individual rods increase by binary fission and spread 

 through the cytoplasm. The young Ascidian oocyte contains {8) 

 five or fewer dome-shaped or hollow spherical Golgi elements — 

 "the primary diffuse condition." As the oocyte grows these come 

 together and form a net-like structure — " the complex condition " 

 — and then later they become once more scattered in the cyto- 

 plasm — " the secondary diffuse condition." 



The Golgi elements may or may not undergo transformation. 

 In Grantia {5), Helix (J2), Limnxa (3), Apantcles {Jf), and Lepus (7) 

 the apparatus probably takes no direct part in yolk formation. 

 In Rana (7) the elements seem to be swollen with a yolk sub- 

 stance, and in Ascidian oocytes (5) many of the Golgi elements 

 enlarge and become fused to swollen mitochondria to form complex 

 yolk bodies. 



Apart from the influence of the mitochondria and Golgi 

 apparatus, yolk granules are formed in some cases as the result of 

 metabolic processes in the ground cytoplasm. This is the case in 

 the sponge, Grantia -compressa (-5), where they seem to develop as 

 small vacuoles in the cytoplasm. These yolk spheres are easily 

 distinguishable from the mitochondria, which are few in numl^er 

 and much larger. . , 



Besides yolk bodies, oil globules have been described in some 

 eggs. Thus in Ascaris (8), where mitochondria enlarge to form 

 the yolk spheres, fat granules are developed as the result of 

 metabolism in the ground cytoplasm. However, in other eggs, 

 e.g. those of Ascidians, which have been specially examined for fat 

 granules, none have been found (9). The black colorization with 

 osmic acid techniques in such cases is due to the presence of lipin 

 in the Golgi elements, mitochondria or yolk bodies. 



Pkevious Work on Oogenesis in Patella vulgaris. 



Gatenby and Woodger in a recent paper (7) refer to oogenesis 

 in Patella. They describe the spreading out of the Golgi apparatus 

 during growth of the egg, and refer to its part in yolk formation. 

 " However the yolk spheres may be formed, be it from the mito- 

 chondria, 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." 



It was with a view to ascertaining the nature of this process 

 that the investigation here described was carried out, at the sugges- 

 tion of Dr. J. Bronte Gatenby and under his supervision, in the 

 Department of Zoology of University College, London. My 

 thanks are due to Dr. Gatenby for his advice and helpful criticism 

 throughout this research. 



