36 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Duplicity in Chick Embryos. — G. W. Tannreutheb (Anat. 

 Record, 1919, 16, 355-67, 6 figs.). A description of some unusual 

 forms of partial and complete duplicity in chick embryos, where the 

 blastoderm divides into several equipotent regions. In one case the 

 blastoderm showed four primitive streaks ; in another the embryo 

 anterior to the primitive streak showed an almost complete duplication 

 of parts ; in a third case there is an almost complete duplication of 

 structures on a common blastoderm ; in another there seem to have 

 been two independent primitive streaks with the anterior ends of the 

 head processes continuous or in immediate contact. J. A. T. 



Absence of Hind Legs below Femur in a Full-term Pig. — 

 M. Carreon {Philippine Journ. Sci., 1919, 14, 201-5, 1 pi). In an 

 otherwise normal litter one member had no hind limbs below the femur, 

 and had also cleft palate. It is 'reasonable to assume that the two 

 abnormal conditions had the same underlying cause. Both show an 

 interrupted growth very early in the development of the pig. Every- 

 thing points to some physico-chemical interference with growth. 



J . A. X . 



Development of Membrane Bone. — Ed. Retterer {C. R. Soc. 

 Biol., 1920, 83, 4-6). The development of the first bony trabeculae in 

 a connective membrane has been studied in the case of the human 

 maxilla. In the mesodermic tissue in which the bone develops there 

 are cells with a granular and reticular framework containing only 

 hyaloplasm. This becomes dense and eosinophilous. The reticulate 

 and anastomosing filaments become more numerous. Thus arises the 

 first intercellular or osseous substance. Between it and the nucleus a 

 .clear cytoplasm appears, which forms the cellular body of the bone-cells. 

 These are separated from the intercellular substance by the formation 

 of a capsule. The inter-cellular or osseous substance increases and 

 differentiates into a framework and an amorphous calcified mass. 



J. A. T. 



Developing Connective Tissue. — Raphael Isaacs {Anat. Record, 

 1919, 17, 243-70, 6 figs.). A study of developing connective tissue in 

 embryos of chick, pig, and man, and of colloids of gelatin, egg albumin, 

 and fibrin under controlled laboratory conditions. The intercellular 

 jelly of embryonic and adult tissue is structurally homogeneous and 

 contains no network of fibrils. The so-called fibrils of connective tissue 

 and neuroglia are fixation artefacts. The fibres of adult tissues are 

 formed by the thickening (concentration increase) of the colloid lying 

 between the fibroblasts. The polarization of the cells, their movement, 

 and the stress exerted on the growing tissue, all serve to give the adult 

 white fibres their arrangement as strands in a bundle. J. A. T. 



Embryological Studies of Indian Fishes. — T. Southwell and 

 B. Prashad {Record!^ Indian Mmeum, 1919, 16, 215-40, 4 pis.). 1. A 

 description is given of two Leptocephalids from the brackish waters of 

 the Gangetic Delta. 2. An account is given of the life-history of 



