1885. ] Embryology. 415 
Intracellular digestion and growth is probably accomplished by 
some of the cells of the epiblast of the blastodermic vesicle, 
which send out pseudopodal processes between the cells of the 
uterine epithelium, as described by Caldwell in the case of the 
blastoderm constituting the yolk bag of the embryos of certain 
Marsupialia. Viviparity has not affected the development of the 
vitellus in the Teleosts, Gambusia, Zoarces and Embiotocide, 
where foetal development is either intrafollicular or intraovarian. 
n albuminoid secretion is said by Blake to be found in the 
temporarily closed gravid ovaries of Embiotocoid fishes ( Journ. 
Anat. and Physiol., 11, 280), and in this family as well as in some 
of the viviparous Elasmobranchs, it seems certain that the young 
developing viviparously are larger than can be accounted for by 
the size of the vitellus of the recently fertilized egg of the same 
species. 
It therefore seems conceivable that the Mammalian vitellus, 
like the ambulatory, prehensile and other organs of parasitic 
organisms, may have been atrophied in consequence of the per- 
fectly parasitic ‘connection subsisting temporarily between the 
maternal organism and the embryo, as was supposed by Balfour. 
—John A. Ryder. 
DEVELOPMENT OF THE SPINES OF THE ANTERIOR DORSAL OF GAS- 
TEROSTEUS AND Lopnius.—The important memoir of A. Agassiz 
before cited, shows that the spines of the anterior dorsal of the 
angler and stickle-back develop in distinct diverticula of the epi- 
blast, a diverticulum being formed for each spine into which 
skeletogenous mesoblast is proliferated from its lower or proxi- 
mal open end. These diverticula soon become free from the an- 
' terior end of the median dorsal fin-fold, the latter, in fact, seems 
to degenerate or be replaced by these diverticula, the first epi- 
blastic diverticula to be developed are more or less translocated 
forwards from their original positions, so that in this way these 
dorsal spines are finally brought to rest on the roof of the skull 
of the adult, considerably in advance of the point where their de- 
velopment began on the nape of the embryo. 
The formation of the singular dorsal appendage of the larva of 
Fierasfer according to Emery’ is developed in a similar way as 
a dorsal epiblastic diverticulum, arising from the anterior end of- 
the median dorsal fin-fold. The singular foliar appendages along 
its sides grow out secondarily. This transitory organ in Fieras- 
fer is, however, much more precociously and rapidly developed 
than the bony, anterior dorsal spines of Lophius and Gasteros- 
teus; its supporting axis is evidently mesoblastic in origin as in 
the latter, but degenerates just about the time of the final — 
morphosis of the animal into the adult condition —/ohn A. Ryder. 
1 ii sistematica, l'anatomia e la biologia delle specie 
Mea pa aperea ene Accad. dei Lincei. Ser. 3, Mem. Cl. di Sci., 
VII, 1880. 
