214 Arthur Willey, 



of symmetry may be brought about in various ways. In the sim- 

 plest cases a disturbance of symmetry is correlated with topographical 

 conditions of space. A more subtle change may be the result of 

 physiological division of labour, accompanying a high degree of 

 specialisation of habits and Organisation. This could take effect, 

 either as implied by Rumley Dawson, by unilateral sexual segre- 

 gation, or as suggested by Doncaster and Marshall, by simple 

 alternate ovulations. 



7. The Amniotic Fluid. 



Having collected a small ' quantity of the amniotic fluid from 

 one of my foetal beavers, I handed the bulk of it over to Prof. 

 R. F. Ruttan of the Medical Faculty, McGill University, who kindly 

 permits me to append the results of his analysis to this paper. 



It appears that there are not many available records of such 

 analyses; and it seemed desirable to fix the biochemical significance 

 of the amniotic fluid of such a typical Rodent as the beaver. 



When the fluid was obtained in April, I added to it a couple 

 of drops of formalin. When Prof. Ruttan received it in September, 

 it had lost a good deal of its original colour but not all. The detail s 

 of the analysis are given in the subjoined table. 



Analysis of Amniotic Fluid of Beaver 

 (R. F. Ruttan, M. D., September, 1911). 



A nearly colorless fluid; pale yellow opalescent, with flocculent 

 precipitate. 



Quantity, 44 cc. 



Specific Gravi ty, 1,0098. 



Reaction, neutral to Litmus, acid to Phenolphthalein, and faintly 

 alkaline to Methyl orange. 



