424 MAINE) AGRICUIvTURAIv EXPERIMENT STATION. I912. 



thus clear that in addition to the shell membranes the glands of 

 the isthmus must also secrete albumen. 



The present investigation has not revealed any visible his- 

 tological difference between the glands of the albumen portion 

 and those of the isthmus. The only differences to be noted ^re 

 in the smaller volume of the tubular glands and the better 

 development of the muscular layers in the isthmus. So far as 

 the present investigation is concerned, no morphological dif- 

 ference between either set of glands in this region and the cor- 

 responding structures in the albumen region have been observed. 

 The one fact of considerable interest, as pointed out below, is 

 the distinct break in the layer of tubular glands between these 

 two regions. The unicellular glands on the other hand are con- 

 tinuous from one region to the other. 



Until the work of Pearl and Curtis it was believed that the 

 only substance formed by the uterus was the calcareous shell. 

 These authors have shown that in addition to this, from 30 to 

 40 per cent, by weight, of the albumen is added to the egg dur- 

 ing its sojourn in the uterus. This thin albumen must pass 

 through the shell and the membrane by osmosis. 



In the present paper it has been shown (p. 420) that the 

 cells of the tubular glands of the uterus differ in appearance 

 from the corresponding cells in other parts of the oviduct. It 

 seems very probable then that the tubular glands are wholly 

 concerned in the secretion of the shell and that the fluid albu- 

 men is secreted by the unicellular glands. The evidence for 

 such an assertion is not complete but it accords with the facts 

 so far observed. 



We have then in the uterus an observed differentiation of 

 the cells of the tubular glands which corresponds to the dis- 

 tinct differentiation in function, viz. : shell formation. On the 

 other hand there is no visible differentiation of the unicellular 

 epithelial glands in any portion of the oviduct with the possible 

 exception of the vagina. We further know that two distinct 

 substances are formed in the uterus, viz. : the calcareous shell 

 and a large portion of the fluid albumen. On this basis of fact 

 it is possible to offer the suggestion that throughout the oviduct, 

 with the exception of the vagina, the unicellular glands are 

 concerned in the production of a fluid or thin albumen. On 

 this view the characteristic difference of each region of the 



