350 THE UNFERTILISED EGG AS A [pt. iii 



The mention of squalene in Table 44 indicates the existence of an 

 egg-constituent, our knowledge of which is of very recent origin. In 

 1 906 Tsujimoto isolated from the liver oils of elasmobranch fishes a 

 saturated hydrocarbon of approximate formula C30H20, and in 191 6 

 published a further study of it. Its properties and constants are given 

 in Table 22. In 1920 he reported that he had been able to isolate 

 it from the egg-yolks of two elasmobranchs, Chlamydoselachus anguineus 

 and Lepidorhinus kinbei, where it made up no less than 13 per cent, 

 of the egg (wet weight) and, in another case, 1 7 per cent, at least of 

 the total fat fraction. There the matter rested until 1926, when 

 Heilbron, Kamm & Owens, taking up the question of its presence 

 in eggs once more, isolated it from the undeveloped yolks of Etmo- 

 pterus spinax, Lepidorhinus squamosus and Scymnorhinus lichia. In the 

 fully developed eggs of the first-named of these three, practically 

 none was present, indicating that it must either have been combusted 

 or absorbed during development. Further researches on the embryo- 

 logical significance of this compound are greatly required. It is 

 possible that some hydrocarbon of this sort may explain certain 

 obscure points in the chemistry of the egg, for instance, the oil 

 extracted by Dubois from the locust's egg {Acridium peregrinum). It 

 contained 1-92 per cent, phosphorus, and was present to the extent 

 of 4*5 per cent, of the wet weight of the egg, no small proportion. 

 Kedzie studied a similar oil which he obtained from the egg of the 

 American locust. 



A question which is perhaps related to the general problem of the 

 egg-oils is that of the oil-globules of the yolks of some of the teleostean 

 fishes. In 1885 Agassiz & Whitman divided all pelagic eggs into 

 those which had the oil-globule and those which had not. But it 

 was soon found that this method of classification was valueless, for 

 the appearance of the globule is rather erratic; thus, although Lota 

 vulgaris (van 'S>2ivs\he\ie) , Brosmius (anon.) and Motella mustela (Brook) 

 were all found to have it, the common pike's egg does not have it 

 (Truman). Ryder first suggested that the oil-globule might have a 

 relation to buoyancy, but Prince, reviewing the whole subject a little 

 later, pointed out that this could hardly be so, for the salmonoid 

 fishes all have them, and yet their eggs never float. Moreover, out 

 of 22 teleost eggs with no globule, 17 are pelagic, while out of 

 24 teleost eggs which have globules, only 15 are pelagic. Ryder 

 replied to this by partially withdrawing his theory, and Mcintosh 



