VIVIPAROUS ANIMALS. _ 407 
These results appear still more surprising, when we consi- 
der that both the absorbing vessels of the foetus, and like- 
wise its nervous system, appear to act but feebly ; as viru- 
lent poisons injected into the pleura, peritoneum, or cellular 
tissue, do not appear to preduce any decidedly deleterious 
effects *. 
The circumstances on which the sex of the foetus de- 
pends, though removed beyond the reach of observation, 
have nevertheless been the subject of conjecture. Many 
years ago, Sir F. H. Eyzes Srixes, in reference to mo- 
neecious and diccious plants, advanced the opinion, that 
“in all cases where the male and female organs are found 
separate, the defect is not in the flower, which I suppose 
to be originally instructed with the rudiments of the or- 
gans of both sexes, but that it arises from some circum- 
stances in the plant, that determines it to blow the one or- 
gan and not'the other +.” An opinion somewhat similar 
is adopted by Sir Everarp Homer, with regard to qua- 
drupeds. He supposes ‘ the ovum, previous to impreg- 
nation, to have no distinction of sex, but to be so formed 
as to be equally fitted to become a male or female foetus ; 
and that it is the process of impregnation which marks the 
distinction, and conduces to produce either testicles or ova- 

‘being turned on one side, at an angle nearly. approaching to a right angle: 
and what may deserve notice, -all of them turned the same way, towards the 
left side. I was urged to rear one of them as a curiosity ; but, conceiving 
that it might grow up rather a disgusting object, 1 had the whole destroyed, 
preserving only the one which appeared to be perfect. That one I kept 
about a month, when it was seized, as well as the mother, with a disorder 
which greatly enfeebled it; and to save the parent, I destroyed the offspring. 
But it was previously discovered, that this also had the tail distorted, and 
turned aside at a considerable angle, although free from the knot which 
-distinguished the other four.”—Lin. Trans. vol. ix. p. 323. 
* M. Macennin, Precis El. ii. p. 448. 
+ Phil. Trans. yol, ‘lv. p. 259. 
