24 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Spermatogenesis in Phalangista vulpina.* — K. von Korff gives 

 a full account of the spermatogenesis in this Marsupial. Most remark- 

 able is the threefold movement of the nucleus before it assumes its 

 definite position. On the whole, the other parts of the spermatozoon 

 are formed as in other Mammals. The author also describes the re- 

 markable spermatozoa of Didelphys which have been inaccurately pictured 

 elsewhere. 



Prepotency in Polydactylous Cats.f — H. B. Torrey describes a 

 family history of cats from which it appears that the total number of 

 digits, as well as the number on each manus and pes went on increasing 

 from generation to generation (three generations), although one parent 

 (the male) was always normal. All the forms were descended from a 

 stray female cat of unknown pedigree, which had six toes on each manus 

 and five toes on each pes. 



Biometric Evidence bearing on Theory of Limb-Origin .%— Bash- 

 ford Dean has made growth measurements of young stages of the 

 Cestraciont shark Heterodontus japonicus, and finds confirmation of the 

 fin-fold theory of the origin of Vertebrate limbs. The pectoral fin is 

 subject to changes with respect to the gravity centre, i.e. physical 

 changes which cause it to become more highly specialised than the 

 ventral fin. The latter is conservative, like the unpaired fins. There 

 is no evidence that the ventral fin is a structure which has shifted its 

 position from in front hindward. In various other ways the author 

 finds confirmation of the Balfour-Thacher theory. 



Notes on Development and Structure of Bradypus.§— L. Simon 

 describes the respiratory system and vascular system of Bradypus tridac- 

 tylus marmoratus. He gives particular details of the arterial branchial 

 plexus, which is almost completely developed in the embryos, and dis- 

 cusses its physiological significance. Two rudimentary teeth — true in- 

 cisors — were found in the lower jaw, and reasons are given for changing 



the adult formula from ~ to ^. A slightly developed " enamel- 



004 004 



organ " occurs, but no Schmeh-Belag ; and no evidence of diphyodont 

 dentition was found. Sebaceous glands, whose presence has been denied, 

 are well developed. In regard to the placenta, the author entirely con- 

 firms the results of Klinkowstrom. 



Development of External Body-Form. ||— Carl Rabl has given us 

 the first part of an atlas displaying beautifully the stages in the develop- 

 ment of the form of Vertebrates — Mammals in the first instance. He 

 calls most of the previous delineations " caricatures," or useless, and 

 the models scheusslich. In dealing with embryos he has used_ platinum- 

 chloride-sublimate or picric-acid-sublimate, and he has stained them 

 with borax-carmin. The results in lithograph are very fine. 



* Arch. Mikr. Anat., lx. (1902) pp. 232-60 (2 pis. and 4 figs.), 

 t Science, xvi. (1902) pp. 554-5. 

 X Amer. Nat., xxxvi. (1902) pp. 837-47 (1 fig.). 

 § Arch. Naturges , lxviii. (19021 pp. 239-61 (2 pis.). 



[| ' Die Entwiekelung des Gesichtes. Tafeln zur Entwiekelungsgeschichte der 

 atif-scrt-n K ; 3rperform der Wirbeltiere,' Leipzig, 1902, vi. and 21 pp. and 8 folio pis. 



