Miscellaneous. 119 



This fact was observed by Agassiz ; but I have been able to go 

 further than that illustrious naturalist. In fact I have ascertained 

 that this disappearance of the albumen is connected solely with the 

 development of the embryo and of the vascular lamella, which, in 

 its origin, is not distinguished from the embryo itself. The albu- 

 men disappears only above the circle formed by the vascular area ; 

 and its disappearance increases like this circle. If by chance, as I 

 have observed in my experiments, the vascular area presents an 

 elliptical form, the empty space produced by the disappearance of 

 the albumen presents the form of an elliptical cylinder, or, more 

 correctly, of a portion of a cone with an elliptical base. Thus 

 during the early part of the development the formation of the vas- 

 cular area is connected with the gradual disappearance of the layer 

 of albumen corresponding to it on the other side of the vitelline 

 membrane. On the contrary, nothing of the kind takes place in all 

 that portion of the blastoderm which is beyond the vascular lamella 

 and surrounds it. 



This led me to think that the albumen necessary for the nutrition 

 of the embryo does not assist in the nutrition of the blastoderm 

 itself. I have verified this prevision by the examination of blas- 

 toderms which had developed without producing any embryo, 

 and which nevertheless had covered almost the whole surface 

 of the yelk. This fact I have several times observed in the 

 course of my teratogenical studies. Under these circumstances the 

 albumen forms a perfectly continuous layer above the blastoderm. 

 We must therefore assume that the blastoderm derives its elements 

 from the yelk, whilst at the commencement of incubation, and, at 

 least, up to the period of the complete closure of the amnios, the 

 embryo is developed at the expense of the albumen. 



I may add that the ascertainment of the disappearance of the 

 albumen is the process that I adopt in my investigations whenever I 

 wish to know whether an embryo is being developed in an egg, a 

 fact which the death and disorganization of the blastoderm do not 

 always allow to be ascertained di^ectl3^ There are, in fact, many 

 circumstances under which the embryo perishes very early, quite at 

 the commencement of the development; and if the egg is not opened 

 until after the lapse of some days, it is often very difiicult to find 

 any appreciable traces of its existence. The disappearance or the 

 preservation of the albumen furnishes a sure means of deciding as to 

 the former existence of an embryo, and to decide whether the 

 blastoderm has produced an embryo or whether it is one of those 

 blastoderms without an embryo, the occurrence of which in my 

 experiments I have just mentioned. — Comptes Eendus, Oct. 30, 1876, 

 p. 836. 



On the Structure and Organization of the Polyphemidae. 

 By Dr. C. Glaus. 



The structure of the body and limbs of the Polyphemidae {Bytho- 

 trephes, Polyphemus, Podon, Evadiie) may be referred in detail to the 



