34- SUMMARY OF CURRENT RESEARCHES RELATING TO 



experiments in breeding mice, guinea-pigs, and rabbits, but with the 

 important qualification stated in the preceding paragraph — a qualifica- 

 tion which really enhances the practical utility of Mendel's doctrine in 

 its everyday application by breeders. 



Radium Effect on Development of Amphibia.* — A. Schaper has 

 proved experimentally that radium rays have a definite inhibitory effect 

 upon cell-division in the frog, etc., also on embryonic differentiation, 

 growth, and regenerative processes. These effects are observable only 

 after a longer or shorter latent period. On frog larvae radium emana- 

 tions had an injurious and finally fatal effect. 



Abnormal Eggs in Fowls.f — J. Kunstler discusses eggs with two 

 separate shells, eggs with a double shell, double eggs, eggs without yolk, 

 dwarf eggs, and so on. A frequent factor is a lack of tone in the 

 oviduct, the usual movements are disturbed, the egg returns on its path. 

 Foreign bodies may ascend from the cloaca and become surrounded by 

 a shell. A mass of albumen may be enveloped in a shell ; and so on. 



Polymorphism of Spermatozoa.} — A. Gravel brings together some 

 of the cases of dimorphic spermatozoa, — in Paludina vivipara, Notom- 

 mata sieboldii, Asellus aquaticus, Pygccra bucephala, Staphylimbs, Cybister 

 roeselii. In Ascaris rnegalocephala there are said to be four forms of 

 spermatozoa, but only one form is capable of fertilisation. Gravel has 

 studied the spermatozoa of Balanus perforatus in which giant forms 

 occasionally occur, apparently in individuals separated widely from one 

 another. These giant spermatozoa may be adapted to cross-fertilisation 

 at a distance ; being stronger, they can move more rapidly, and further. 



Factors of Morphogenesis. § — Tad. Garbowski discusses Trichoplax 

 adhcerens and other Mesozoa, the processes of gastrulation and ceeloni- 

 formation, and the scope of physiological morphology. 



He rejects the homology of the germ-layers, the gastraea -theory, the 

 ccelom-theory, and much more. He insists that a scientific interpreta- 

 tion of the pedigrees of animals must be based on an observational 

 and experimental study of the formative processes which actually occur 

 in morphogenesis. 



(Estrous Cycle in Ferret.|| — F. H. A. Marshall finds that the female 

 ferret is moncestrous, and may have one, two, or three sexual seasons 

 within a year. The " heat " periods, however, are usually restricted to 

 the spring and summer months. During the oestrous cycle the non- 

 pregnant uterus experiences in succession periods of rest, of growth, of 

 degeneration, and of recuperation. The changes occurring during these 

 periods afford proof of the homology between the menstrual cycle of 

 the primates and the oestrum of the lower mammals. Ovulation occurs 

 probably at the commencement of the oestrous period, but only as a 



* Anat. Anzeig., xxv. (1904) pp. 326-37. 



t Mem. Soc. Sci. Bordeaux, ser. 6, iifc (1903) pp. 65-72 (7 figs.). 

 X Tom. cit., pp. 273-9. 



§ Morpbologische Studien, Als Beitrag zur Methodologie zoologischer Probleme. 

 4 to. Jena (1903) vii. and 189 pp., 6 pis. 



|! Quart. Journ. Micr. Sci., xlviii. (1904) pp. 323-45 (3 pis.). 



