328 THE UNFERTILISED EGG AS A [pt. iii 



attempt to throw light on this question, prepared pure samples of 

 chitin from the newly fertilised eggs ofAscaris megalocephala by boiling 

 them with strong potash, and identified the chitin chemically, 

 isolating glucosamine hydrochloride from it. Remembering that 

 Weinland showed that chitin is probably formed from glycogen 

 during insect metamorphosis, Faure-Fremiet estimated the glycogen 

 in the Ascaris eggs before and after fertilisation. Before fertilisation 

 there was an average amount of 20 gm. per cent, dry weight, but 

 afterwards only 4-67, the extreme values being 5-91 and 3-23, so 

 that no less than 17 per cent, of glycogen had disappeared. Estima- 

 tions of chitin in the egg-envelopes after fertilisation gave results of 

 between 8-3 and 10-7 per cent, dry weight of glucosamine (calculated 

 as glycogen) with an average of 9-23. The total glucose, then, in the 

 fertilised eggs was 12-83 to 15-08, as against 20-0 in the unfertilised 

 ones, a loss of 7 to 9 per cent. All the glucose lost, therefore, could 

 not have transformed itself into chitin, but must have had some other 

 destination, perhaps butyric and valerianic acid if Weinland's view is 

 correct. The eggs o^ Ascaris have also an " ovospermatic membrane", 

 but for the discussion of the significance of this reference should be 

 made to the memoir of Faure-Fremiet, and nothing is known about 

 it chemically. Their third membrane, the internal one, would seem 

 to be composed to a large extent of ascaristerol (see p. 352), for the 

 histological evidence demonstrates a collection of the ascaristerol 

 globules at the periphery of the cytoplasm. After fertilisation, Faure- 

 Fremiet found the saponification number of ascaristerol lowered from 

 199 to 145, from which he concluded that its constitution had been 

 slightly altered. Zavadovski has also described the egg-shells of many 

 nematodes. • 



Neumeister, who found more than 5 per cent, of sulphur in the 

 shells of the reptiles, Calotes jubatus, Ptychozoon homalocephalus, and 

 Crocodilus biporcatus, concluded that they consisted of a true keratin, 

 and the reactions given by the egg-membrane protein of a mono- 

 treme, Echidna aculeata, led him to the same conclusion in that case 

 also. Table 9 gives the figures which he obtained for the calcium 

 and other constituents of some of these egg-shells, as well as the 

 very similar investigations of Wicke & Brummerstadt on Alligator 

 sclerops. From these fragmentary results, it would seem that the egg- 

 membrane protein is here keratin, and a quantity of calcium is 

 secreted into the membrane by the animal, varying in amount from 



