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connective tissue. Round older eggs he says the mesoarium grows 

 out into a diverticulum, so that they come to lie in a stalked pocket- 

 shaped appendage of the mesoarium. No one from reading this could 

 understand the exact relations of the ovum to the mesoarium, which 

 are clearly described in my paper. Müller next describes ovarian 

 eggs of 18 mm length. These are surrounded by two connective tissue 

 envelopes ; the outer is thin and only closely connected with the inner : 

 the former is a continuation of the mesoarium. The second or inner 

 is firmly adherent to the testa which lies beneath it. The inner surface 

 of the inner membrane forms a Membrana propria , in contact with 

 which is a layer of cells towards the middle of the ovum single, tow- 

 ards the poles many cells deep. Towards the middle of the ovum the 

 cells of this layer are square or cubical, toAvards the poles more cylin- 

 drical and forming 3 or 4 layers. In the middle of the white pole of 

 the egg this cellular layer shows a conical hollow • I mm deep Avith a 

 funnel shaped opening directed toAvards the nucleus and svirrounding 

 protoplasm, this opening being the micropyle. The only other stage of 

 the ovum Avhich Müller describes is that of the fertilized ova obtained 

 from the Göteborg Museum. These possessed the polar threads, and 

 Avere fastened together by them. The testa of these eggs shoAved no 

 trace of the inner or outer connective tissue envelope, Avhich must have 

 disappeared completely like the enamel-organ of teeth Avhen the 

 enamel is completely formed. Müller then describes the blastoderm 

 of these ova. 



It is perfectly obvious from the above that Müller considered the 

 follicular epithelium to be the testa, the membrane Avhicli surrounds 

 the deposited ovum: the micropyle he describes in the large ovarian 

 ovum is a cavity in the epithelial layer : in the ovarian ovum he did 

 not see the true vitelline membrane or zona radiata at all, and in the 

 deposited ovum he thought the vitelline membrane AA^as the follicular 

 epithelium or cellular layer of the earlier stage, as is evident from his 

 comparison of the egg membrane Avith the enamel of teeth. Moreover, 

 although Müller states that the outer of his tAvo connective tissue 

 layers Avas continuous with the mesoarium he evidently considers them 

 as belonging to tlie ovum, and concludes that they disappear by de- 

 generation. Müller gave no account AA'hatever of the develo])ment of 

 the polar threads. 



In my paper I have shown that there is only one layer of con- 

 nective tissue round the egg, and that this belongs to the ovary where 

 it remains after the ovum is shed, forming a corpus luteum. I have 

 also described completely the structure and development of the vitelline 

 membrane which Müller in the ovarian ovum did not see and in the 



