354 THE UNFERTILISED EGG AS A [pt. m 



in their reactions to staining methods, Fels in 1926 confirmed this 

 difference for the human egg-cell, some specimens of which showed 

 a strong lipoid-reaction (Ciaccio and Smith-Dietrich methods) in the 

 nucleolus while others did not. Fels' illustration is certainly striking. 

 Leupold had already put forward the view that eggs whose nucleoli 

 were rich in lipoids produced females, and the remainder males, but 

 all the evidence, however, is against sex-dimorphism in the mam- 

 malian egg (see Parkes' review). These observations, together with 

 those of Pollak on the presence of Reinke's crystals in the egg of 

 Macacus rhesus, and similar work by Limon and" von Ebner (on 

 Cerrus capreolus), are all that we have on the chemical constitution 

 of the mammalian egg-cell. 



Closely connected with the lipoids of the egg is the distribution 

 of phosphorus compounds in it and Table 45 gives what is known 

 upon this subject. It is interesting to see how the phosphoprotein 

 phosphorus varies, in some eggs being very large in proportion to 

 the total phosphorus, in others being almost insignificant. Masing 

 was wrong in saying that the echinoderm egg has none at all, for 

 Needham & Needham in 1929 observed quite a high percentage 

 in the &gg of the sand-dollar. It is significant in view of what 

 has already been said about the pre-eminence of birds in storing 

 fat in their eggs, that the hen's egg has 20 per cent, more 

 phosphorus in lipoidal form than any other egg investigated. 

 The fishes rank in this respect with the echinoderms and annelids, 

 little diflference being noticeable between alecithic and lecithic eggs. 

 Perhaps this famous distinction involves neutral fat rather than 

 lipoids. 



It is to be noted from Table 45 that the inorganic phosphorus 

 content of eggs is very variable; in many cases almost none is present, 

 but the haddock's ^gg seems to have no less than 20 per cent, of the 

 total phosphorus in this form. About the same proportion is present 

 in the nematode egg, ii Ascaris can be taken as representative. Faure- 

 Fremiet was able to identify the calcium phosphate in the egg-cyto- 

 plasm with the "hyaline balls" described by van Beneden, using 

 various histochemical reactions (McCallum, Prenant, etc.). Pure 

 calcium phosphate, according to Faure-Fremiet, accounts for 0-4 to 

 0-6 per cent, of the dry weight of Ascaris eggs, an inconsiderable 

 amount in view of the share it takes in the appearance of the cyto- 

 plasm as a whole. 



