604 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ance of the mesoderm and the formation of the amniotic folds; and 

 (3) the process of gastrulation and the origin of the allantois. He dis- 

 cusses in particular the so-called inversion of the germinal layers (or 

 " entypy of the germinal area " by a process of delamination), and main- 

 tains its entire distinctness from the belated gastrulation. 



Teeth of Two Dentitions in a Dermoid Cyst.* — H. Bluntschli 

 describes a dermoid cyst from the human ovary which was remarkable 

 in showing a number of typical milk-teeth (incisors and canine of the 

 lower jaw), and, along with these a number of teeth (premolars) of the 

 permanent set. The remarkable feature is the simultaneous occurrence 

 of the two kinds of teeth, for normally the permanent premolars do not 

 appear until the milk-incisors have been replaced. 



Ovary in Hybrid Birds.t — Heinrich Poll has studied the state of the 

 ovary in crosses between Anas boscas var. doin. and Cairina moschata, 

 Fuligula fuligula and Mareca penelope, and eighteen other cases. Some 

 female hybrids lay eggs which develop ; others are quite incapable of 

 reproduction, though they may sometimes lay eggs. 



In all the quite sterile hybrid females there is a constant peculiarity, 

 namely the absence of small reserve follicles in the adult. This is seen 

 in hybrids of Anas and Cairina, Lampronessa and Metopiana, Netta and 

 Polionetta, etc. In other cases even the just mature bird may show no 

 trace of follicular apparatus, as in Mareca and Dafila, Fuligula and 

 Mareca. The degeneration may go even farther, as in M. penelope and 

 Lampronessa sponsa. 



There are reserve ova in the female and trimitosis in the spermato- 

 genesis of the male in cases like Mareca penelope and Chaulelasmus 

 streperus, Alopochen segyptiacus and Tadorna tadorna, Streptopelia risoria 

 and Turtur tnrtur, Garcluelis carduelis and Serin us canarius. Associated 

 with the absence of reserve ova and the further degeneration of the 

 ovary in the sterile hybrid females, there is a corresponding reduction 

 (dimitosis, monomitosis, and apomitosis) in the spermatogenesis of the 

 hybrid males. 



Fluctuations in Growth of Fowl's Comb.J — Geoffrey Smith finds 

 that the correspondence of the comb-increase in hens with periods of 

 egg-laying is invariable, both in young and adult hens. The increase 

 of the comb in the hen is due to a fatty infiltration of the central 

 connective-tissue core of the comb ; the decrease in the comb is due to 

 the abstraction of the fat. The cock's comb contains only comparatively 

 small quantities of fat in the central core, the substance of the comb 

 consisting principally of fibrous connective-tissue. The cock's comb 

 does not exhibit marked fluctuations as the hen's does. 



The increase in the comb is not accompanied by a rise in general 

 body-weight, though such a rise usually occurs some time before the 

 increase and fat deposition occur. The explanation of the fatty infiltra- 

 tion of the comb is found in the fact that at the egg-laying periods the 



* Morphol. Jahrb., xliii. (1911) pp. 345-57 (3 figs.). 



t Arch. Mikr. Anat., lxxviii. (1911) Festschrift Waldeyer, 2te Abt., pp. 63-127 

 (4 pis. and 1 fig.). 



X Quart. Journ. Micr. Sci.,lvii. (1911) pp. 45-51 (4 pis. and 5 figs.). 



