140 Transactions of the Society. 



accordance with our own observations ; but we differ as to inter- 

 pretations. The archoplasm has no direct connexion with the 

 formation of the yolk, though we recognize that it is in the region 

 of the archoplasm that the mitochondria are found and grow most 

 rapidly ; this however does not allow us to conclude that the 

 archoplasm may be called a vitelline body, or that it grows or 

 behaves in a way which resembles the true yolk nucleus of an 

 Ascidian. While we acknowledge that the mitochondria form an 

 elongate matted body in the region of the archoplasm, during one 

 period of the oogenesis, it is extremely doubtful whether this body 

 should be homologized with the Ascidian yolk nucleus. We con- 

 clude that there is not satisfactory evidence that a true " yolk 

 body " or " nucleus " exists in Amphibia. 



This temporary conclusion is in agreement with the view 

 expressed by Dubuisson (7), with whose work Lams disagrees. 



In insects such as Steiiohothrus, the Golgi elements appear to 

 be separate from the yolk. In Dtjtiscus, ISTusbaum-Hilarowitz (31) 

 has shown that the Golgi apparatus and the formation of yolk 

 spheres are unconnected with each other. In Dytiscus with 

 Champy-Kull's method the yolk spheres are fuchsinophile (see 

 page 136). We have lately seen some of Mr. L. Hogben's prepara- 

 tions of Periplaneta ovaries, from which it seems clear that some, 

 at least, of the yolk sj^heres of the cockroach ^gg are formed within 

 the nucleus, possibly from the nucleoli, and finally shot out into 

 the egg cytoplasm. 



Formation of Yolk in Ascidian Oogenesis. 



According to Hirschler (£?) yolk granules of Ascidian ova are 

 formed by two processes : — 



(1) A simple metamorphosis, and enlargement of the mito- 

 chondrium to form a new body, and (2) a secondary fusion of 

 many of the Golgi elements with these swollen mitochondria, to 

 form a compound structure, and a swelling up of the Golgi elements 

 themselves. 



He tells us '' that the yolk spherules* which represent the 

 reserve material of the developing embryo consist of mitochondrial 

 and Golgi apparatus substance. During embryonic development 

 a more vigorous growth and regeneration of the apparatus, and 

 perhaps of the mitochondrial substance, also very probably takes 

 place, as the investigations of Van der Stricht on Noctula would 

 suggest. This regeneration would, as we suppose, come about in 

 the following manner: — The yolk gives off the apparatus and 

 mitochondrial structures present in small quantity in the dividing 

 Qgg cell, so that the dissolution and using up of the yolk during 

 embryonic development would thus in great part be attributed to 

 the giving off of these substances." 



