36 SCIENCE PROGRESS 



alternate. It is probable that only one pair of factor differences 

 is involved. 



Other papers include : 



Duerden, "Inheritance of Callosities in the Ostrich" [Amer. Nat., vol. 

 liv. No. 633, Aug. 1920) ; Kuntz, " Experimental Observations on the 

 Histogenesis of the Sympathetic Trunks in the Chick" {Jour. Comp. Neur., 

 vol. xxxii, No, 3, Dec. 1920) ; and Nonidez, " Studies on the Gonads of the 

 Fowl : I. Hematopoietic Processes in the Gonads of Embryos and Mature 

 Birds " {Amer. Jour. Anat., vol. xxviii. No. i, Nov. 1920). 



Hausman has fairly recently published a series of papers 

 on the hair of mammals, of which two fall in the period under 

 review, viz. : "A Micrological Investigation of the Hair 

 Structure in the Monotremata " {Amer. Jour. Anat., vol. 

 xxvii, No. 4, Sept. 1920), and " Structural Characteristics of 

 the Hair of Mammals " {Amer. Nat., vol. liv, No. 635, Dec. 

 1920). In the Monotremes several different types of hair are 

 to be found upon the body. The characteristic type is 

 flattened, and of the variety encountered in the shield hair of 

 Ornithorhynchus. This animal possesses also a fur hair, of the 

 same general type as in other mammals, and this is lacking in 

 Tachyglossus. Mammal hairs are either circular or oval in 

 section ; the former is usually straight, and the latter kinky or 

 curly. Each mammal is characterised by its own special 

 type of hair. The second paper provides illustrations of a 

 number of the common types, and also a discussion of the 

 methods of investigation. The discussion of the much-vexed 

 question of the islets of Langerhans has been taken up by 

 Saguchi in " Cytological Studies of Langerhans's Islets, with 

 special reference to the Problem of their Relation to the Pan- 

 creatic Acinus Tissue " {Amer. Jour. Anat., vol. xxviii, No. i, 

 Nov. 1920). As a result of studying the specific granules 

 they contain, the mitochondria, lipoid granules, urano-argen- 

 tophile apparatus, argentophile granules, etc., the author 

 concludes that they are to be regarded as modified acinar 

 tissue, and he distinguishes five types of cell among them 

 which he designates a, b, c, d, and e, some of which are inter- 

 mediate between true islet and acinar cells. " The develop- 

 ment of the veins in the domestic cat {Felis domestica), with 

 especial reference (i) to the share taken by the supra-cardinal 

 veins in the development of the postcava and azygos veins, 

 and (2) to the interpretation of the variant conditions of the 

 postcava and its tributaries as found in the adult " has been 

 worked out by Huntington and McClure {Anat. Rec, vol. xx, 

 No. I, Dec. 1920). The title explains the contents of the 

 paper, which is fully illustrated by coloured plates of wax 

 reconstructions, and a composite diagram gives the clue to the 



