538 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Monotremes. |It is not known whether the condition observed was 

 unusual or not. 



Development and Structure of Fins.* — E. S. Goodrich deals with 

 the development, structure, and origin of the median and paired fins of 

 fishes. He has made a series of observations on embryos of Scyllium 

 canicula, and concludes that the development of the median dorsal fins 

 is essentially similar to that of the paired fins. They arise as longi- 

 tudinal folds into which grow buds from the myotomes. There is early 

 concentration, chiefly due to the body growing faster than the fin. 

 Neither the study of development nor of the adult structure affords any 

 definite evidence that the primitive metamerism of the musculature is 

 lost. All the fins remain throughout development in approximately the 

 same position. Apparent change of place may be brought about by 

 concentration being greater in the one direction than in the other. 

 This is especially the case with the dorsal fins : the results give strong 

 support to the lateral fold theory of the origin of paired fins, and their 

 general bearing is fully discussed. 



Functional View of Development^ — M. E. Henriksen propounds 

 a functional view of development in relation to which Weismann's theory 

 of the structure of the germ-plasm is unnecessary. According to this 

 view, " the adult organism is not predelineated nor singly predetermined 

 in the egg, but develops by progressive steps, one part dependent on the 

 other, to establish proper relations within the cells as well as among the 

 cells, and when properly nourished and in proper environment it will 

 establish the equilibrium of the species ; it will form a body much like 

 that of the parent." The physiological interactions of the parts of the 

 cell constitute the all-determining factor for establishing the relations 

 between the blastomeres, and thus in a progressive manner the organism 

 reaches a state of equilibrium peculiar to that of the species. Since each 

 successive step in development is dependent on the preceding, it neces- 

 sarily follows that the ontogeny must be a shortened recapitulation of 

 the phylogeny of the organism. In support of his views the author 

 discusses the results of recent experimental embryology, showing that 

 inheritance is independent of structure — is, in fact, a functional problem. 



Text-Book of Teratology.! — E. Schwalbe has completed the first 

 part of a text-book on teratology, which will be welcomed by many 

 investigators. He discusses the facts in the light of embryology, com- 

 parative anatomy, and pathology. We may call attention to the chapters 

 on experimental teratology, on regenerative and regulative processes, on 

 the formal and causal genesis of abnormalities, and on their classification. 



Bull with a Supernumerary Limb.§ — Jose Rioja y Martin com- 

 municates two photographs of a bull with a supernumerary leg of large 

 size, arising dorsally above the shoulder, curving downwards and 

 forwards, and ending in five huge curved claws. 



* Quart. Journ. Micr. Sci., No. 198 (1906) pp. 333-76 (5 pis.). 



f Biol. Centralbl., xxvi. (1906) pp. 18-24, 33-7. 



% Die Morphologie der Missbildungen des Menschen und der Tiere. Ein 

 Lehrbuch fur Morpbologen, Physiologen, praktische Aerzte und Studierende. 

 I Teil. Allgemeine Missbildungglebre (Teratologic). Jena, 1906. 



§ Boll. B. Soc. Espafi. Hist. Nat., v. (1905) p. 415 (2 pis.). 



