332 Transactions. — Zoology. 



before distension by fluid, and that it corresponds with the 

 horny egg-shell of oviparous forms. The fact of its being 

 formed before the partitions, to which in later stages it ad- 

 heres so closely, is worthy of notice. 



One very striking feature in the development of Mustelus 

 is the extensive growth of the embryo (including the yolk-sac) 

 taking place during intra-uterine life. As stated above, the im- 

 pregnated egg is only about 43mm. long by 16mm. in diameter, 

 while the ripe foetuses are fully 220mm. (9in.) long, and 25mm. 

 (lin.) across the head. As there is no vascular connection be- 

 tween parent and offspring, and as the latter is separated from 

 the wall of the uterus by the pseudamniotic fluid, this fact is 

 one of considerable interest. 



In the paper already referred to it is stated, as the result 

 of a rough analysis, that the pseudamniotic fluid contains a 

 large proportion of urea, but little or no proteid matter. The 

 following extract from a letter from my friend Professor 

 Liversidge gives a more accurate account of the composition 

 of the fluid. The sample sent to him was mixed with an 

 equal volume of rectified alcohol. 



" I have at last given your pseudamniotic fluid of Mustelus 

 ■antarcticus a little attention. When you sent it last year I 

 was afraid that it had been so long bottled (since the 10th 

 October, 1883) as to be not worth examination ; but as I got a 

 croj) of crystals almost at the first experiment I went on. 



"There was a good deal of flocculent sediment, but the 

 fluid above was fairly clear. 



"1. To litmus the fluid was faintly alkaline. 



"2. On slow evaporation it left crystals somewhat re- 

 sembling urea, and a few isolated crystals of triple phosphate. 



"3. It yields crystals with oxalic and nitric acid resem- 

 bling the oxalate and nitrate of urea ; but I do not attach much 

 importance to crystals formed in complex oi'ganic fluids — i.e., 

 to their form. 



"4. With fuming nitric acid, CO. (and probably N) is 

 given off ; did not test expressly for N gas : — urea. 



" 5. With Hg2N0,, = white ppt. = urea. 



" 6. With Hg2N0:, and excess of NaCl, no ppt. = urea. 



" 7. With Hg and HNO3, from which coloured fumes were 

 being evolved, the addition of sonie of the pseudamniotic fluid 

 rendered the gases colourless ; .•. COo and N were evolved : 

 = urea. 



" 8. Uric acid was found to be absent. 



" 9. Phosphoric acid abundant. ' 



" 10. Magnesia abundant, and probably present as triple 

 phosphate. 



"11. Lime present. 



