SUMMARY OF CURRENT RESEARCHES. 161 



have larger internal organs except in the case of heart and lungs, which 

 are usually more strongly developed in cocks. He applies the phrase 

 organic sexual dimorphism to the relation of female mean weight of 

 internal organs to the male mean weight of the same. The ratios vary 

 with the different organs (kidney, spleen, liver, pancreas, gizzard, cseca, 

 &c), and the dimorphism is not in any simple way connected with egg- 

 laying or increase in gross weight. Houssay shows the curious changes 

 brought about by carnivorous diet, but as yet the results are too complex 

 to yield a satisfactory conclusion. 



Regeneration in Newts.* — August Weismann reports the results 

 of experiments made under his direction by Egon Breinig. In four 

 cases the oviduct was removed, and no regeneration followed. Experi- 

 ments with the vas deferens gave the same negative result. In the case 

 of lungs, from which the end was cut off, there was a slight terminal 

 expansion of the organ, but this may be regarded as the mechanical 

 result of continued function. Weismann contrasts these results with 

 the well-known regeneration of the eye — an organ which in natural 

 conditions is liable to be injured by water-beetles, dragon-fly larvae, and 

 other enemies of the newts. 



Torsion of Bird-Embryo. f — A. Weber has investigated the early 

 stages of torsion on the longitudinal axis as observed in normal embryos 

 of birds, but he has got much help by a study of two cases where the 

 amnion was wholly absent, — a very rare anomaly. 



G-astrulation of Double-Development in Trout.} — F. Schmitt has 

 made a careful study of this process. It occurs in blastoderms which 

 are not larger than the normal nor richer in germinal material. The 

 occurrence of double-embryos cannot be interpreted on the concrescence- 

 theory without auxiliary hypotheses. A short summary is given by the 

 author, but we must be content at present with a mere reference. 



Curvature of the Spine in Fishes. § — J. Pellegrin brings together 

 a number of cases of abnormal curvature and similar abnormalities in 

 the vertebral column of Teleosts. He alludes to the sole (Howes), the 

 perch (Howes), Coxitis fossilis (Giard), the mackerel (Petit), Mullus 

 surmuletus, Mugil capito, Trigla hjra (Moreau), and so on. To what 

 are these malformations due ? According to Pellegrin, they are referable 

 to muscular variations which influence the skeletal development. 



6. Histology. 



Cell-Division. H— A. Bethe contrasts the mechanical filament-theories 

 (Fadentheorien) with the dynamical centrosome-theories to the advan- 

 tage of the latter. He brings forward" a number of facts described by 

 various investigators which cannot be interpreted on the mechanical 

 theory. The field is really left to the dynamical theories, that is to 

 those interpretations which do not credit the achromatin threads with 



* Anat. Anzeig., xxii. (1903) pp. 425-31 (3 figs.). 



+ Journ. Anat. Physiol, x .xix. (1903) pp. 75-92 (1 pi. and 16 figs.). 



J Verh. Deutsch. Zool. CJes., xii. Vers. (1902) pp. 64-83 (7 figs.). 



§ Bull. Soc. Zool. France, xxvii. (1902) pp. 215-9 (3 figs.). 



|| Internat. Monatschr. Anat. Physiol., xix. (1902) pp. 118-28. 



April 15th, 1903 h 



