3 
4iffererrtiation, while they do not appear in females till } cr M 
•tiich i. n r ti e t «-■> of birth* Lillie (• f * ) alienr. ti at toe horacne 
is already effective in a free- -riin or S.?5 ca«# and pcinto out that 
sy.sOtic ftos-dctaminlng factor:} aro ol«© ir. a e rtain degree aex- 
differentiating factors in ssasssals as In .resets, and that, nhlle 
in th ala these factors ere irol I - reinf • 
hormone action till abo t the tiro of birth at aarll rt, is *ho sals 
they are reinforced early# e seers to thin that th© hc^no ray 
bo introduce in the care of the free-martin before ©axual differ - 
tiation, but trie can hardly be true for the appearance °* * n t- r ~ 
atiti&l cells i-s in Itself a sexual differentiation, an: ir t o 
froo-' irtin, while tna ar.-.t ;is iocs t, fce pUc as early as the 
1.5 c.3# sta...e, Lillie (* )• ar.d pr bably as early, at* 1.0 c~ ., 
confirr-ea in t o writer* cello, tics# th hornene cannot be intro- 
uucad before the appoara.ee of the colls that produce it. In the 
free-cartin while the effects aay appear early in esse car *c and 
are the case effect.- as produced in t r* sale, in other cases, 
they dc aot appear till the ferric ha» under.. ore s coca id arable 
aroorst of sexual differentiation* Prscir ubiy t o hor~o- o has 
net been introduces till near th .t stars• 
To date so exact and ninuto a.-.to: ic>l ccn c isons of the 
our l i. r stages' of normal ala and fe^sele o bryonlo and foetal 
^.evelo parent hare been rsade with reference to the 1 fferertiatien 
of ti,e sex-ducts and oro*.enit«l canals. T iu, wifi: the sr*~e .sort 
of >tu:ly of tho r: -rurtin. in nectar.ary* o 4 ” cc- m as a W:ir 
for tho oor ‘ieto of toe course of the freo-cartln con¬ 
dition iind Its variation. 
