128 SUMMARY OF CURRENT RESEARCHES RELATING TO 



feather in connexion with the moult, in the same manner as does any 

 other follicle of the body. The process of moulting re-activates the 

 follicle which has been brought into a quiscent state by successive 

 feather removal. 



3. The precise pattern is usually reproduced each time with extreme 

 fidelity of detail. But if the feather is removed from the follicle as 

 soon as it is fully grown, thus forcing continued regenerative activity, 

 the pattern tends gradually to break up. Perhaps the pattern gene is 

 represented in each follicle by a strictly limited amount of material. 



■f. The secondary sexual feathers of the male, such as the saddle 

 hangers, only appear as adult plumage. The same follicles which produce 

 these, produce as juvenile plumage only undifferentiated body feathers. 

 If the juvenile feather be removed apart from the normal moult, the 

 next feather produced by that follicle will be the secondary sexual 

 feather, and not a feather of the juvenile type. After that all the 

 regenerations are of the sexually differentiated feather. 



Visceral Clefts in Chelonians.* — H. v. Alten has studied embryos 

 of Ghrysemys marginata with particular reference to the visceral clefts 

 and the " branchiogenic " structures which arise from the epithelium of 

 the clefts, namely thymus, "epithelial bodies," and supra-pericardial 

 bodies. There are five pairs of branchial pouches and a paired diverti- 

 culum which is constricted off to form the supra-pericardial bodies. 

 These are closely associated with the last two pairs of pouches, but 

 are at first quite distinct. Later on, the wall of the gut forms a 

 lateral diverticulum bearing the fourth and fifth pouch and the supra- 

 pericardial body, so that the last looks almost like an appendix of the 

 fifth pouch. 



The first, second, and third pouches open to the exterior. The 

 fourth comes close to the ectoderm, but no opening was seen. The first 

 pouch forms a dorsal epithelial thickening in close relation to the facial 

 ganglion, and it also forms a " branchial cleft organ." The second forms 

 a dorsal epithelial thickening in close relation with the glossopharyngeal, 

 and there is also a ventral diverticulum. The third forms a marked 

 epithelial thickening in relation to the vagus, and a ventral diverticulum is 

 constricted off. The close resemblance between the origin of the supra- 

 pericardial bodies and that of the fourth and fifth branchial pouches 

 leads the author to the view that there are six pairs of these pouches, as 

 some maintain for Teleostei, Anura, Urodela, and Lacertilia. 



Brooding Instinct in the Domestic Fowl.p— R. Pearl publishes 

 an account of observations on the brooding instinct of the domestic fowl 

 in its relation to egg-production. Broodiness normally constitutes one 

 element in the cyclical reproductive activities of the female. It recurs 

 with greater or less regularity following periods of laying. The degree 

 of intensity of the brooding instinct, both in respect of its objective 

 manifestations and of its physiological basis, may vary considerably at 



* Ber. Nat. Ges. Freiburg, xx. (1914) pp. xcix-cv. 

 t Journ. Animal Behaviour, iv. (1914) pp. 266-88. 



