YOLK FORMATION 153 



have followed, notably Gatenby (on Saccocirrus), Ludford [Limncea 

 and Patella), Nath and collaborators (Scorpions, Lithobius, 

 Luciola, and Periplaneta), King (on Lithobius), Gresson (on 

 Tenthridinida^), Spaul (on Nepa). There are, however, two distinct 

 views contained here, for several workers believe the extrusions 

 to be directly metamorphosed into yolk while other workers (or 

 the same workers on different material) conceive of an indirect 

 relationship. In the minority we find Brambell (on Patella) and 

 King (Oniscus) finding the mitochondria swelling up to form 

 protein yolk ; Weiner (on Lithobius and Tegenaria) and Stoepoe 

 (Nepa) derive this yolk from the Golgi bodies, as does Harvey also 

 (on Ciona (indirectly) and Carcinus). Nath finds the cytoplasm 

 the source of albuminous yolk in Spiders and Koch does the same 

 in Lithobius. 



Thus in regard to the formation and source of the albuminous 

 yolk, no general statement can be made. 



There are only a few cases in which comparisons can be made 

 between different sets of observations on the same material. 

 This does tend to eliminate the personal bias to a certain extent, 

 although workers in the same school of thought are liable to the 

 criticism of having the same preconceived ideas. 



Comparisons in the case of the Mollusca, Helix, Limncea and 

 Patella show that there is quite a considerable amount of difference 

 of opinion at any rate concerning the origin of the albuminous 

 yolk. The four workers on Lithobius show wide divergencies as 

 to the processes involved. Even Nath and King differ over the 

 origin of the albuminous yolk (rather more than the summary 

 indicates ; vide Addendum to King's paper (69)). 



Summarising, it would appear that no definite conclusion can 

 be come to at the present time. It does not apparently assist 

 matters to say that the majority of workers are of the opinion 

 that the fatty yolk is produced by the Golgi bodies and the albu- 

 minous yolk derived from the nucleolar extrusions. The weight 

 of evidence produced by other workers is sufficient for us at least 

 to conclude that that is not the whole story. 



To return to the suggestion of Hogben's referred to above, that 

 the yolk is probably produced by an interaction of the various 



