704 EMILY RAY GREGORY, 



of the system the tubules are already formed" ; it is plain that his 

 material was not young enough to determine finally their homology. 



With the imagination I can suppose that the external glomera may 

 by entering the later closed otï tubules become the glomeruli of the 

 mesonephros, as is held by some. Felix in the discussion over 

 Myxine (in : Anat. Anz., V. 13, p. 593) says : "Die Vomiere kann 

 also einen Glomerulus besitzen, der vollständig mit dem der Urniere 

 übereinstimmt", but I can find no such relation in my material. If 

 they were one and the same structure, at the point where the glo- 

 meruli first appear, they should be in the same condition as the glomus 

 but such is not the case. The glomerulus appears as described above, 

 as a large tuft of cells developing from the inner dorsal wall of the 

 tubule. These cells are very round while outside of the tubules the 

 glomera do not contain tissue. 



Here I am in harmony with Maas, who says, '97, p. 498: "Das 

 Verhältniss, das die Vornierencanälchen zum Glomus haben, diesen 

 letztern Beziehungen der segmentalen Urnierencanälchen zu den ein- 

 zelnen Glomeruli homolog zu setzen, dürfte wohl unmöglich sein", and 

 again, p. 501 : "das 'Glomus' der Vorniere, so wie es entwicklungs- 

 geschichtlich gefunden wird, und dessen Hineinragen ins Cölomdivertikel 

 gerade zum Vergleich mit dem Glomerulus in der BowMAN'schen 

 Kapsel Anlass gegeben hat, eine ganz secundäre cänogenetische Bil- 

 dung ist und mit dem Wesen einer Vorniere gar nichts zu thun hat." 

 Semon holds very strongly to the close relationship, but a study of 

 his figures, '92, figs. 1 and 2, shows such dissimilar structures that 

 it seems to me impossible to homologize thorn. 



In connection with the Cölomtasche described by Price, '97, I 

 may say that in some of my embryos when the basis of the anterior 

 limb has grown and folded down so as to form a small and sharp 

 corner with the kidney lobe, simulating a tubule, I find occasionally 

 that the endothelium has thickened here and looks as if a second 

 one would form or was forming there. This appearance is soon lost, 

 however, and in no case could a true tubule be demonstrated. 



Incidental Observations. 



In the course of such a study and the examination of so many 

 series of shdes, I have necessarily noticed interesting points not related 

 to my subject. It may be worth while to mention one or two of 

 these. 



The earliest stages were exceedingly interesting for cell study. 



