534 SUMMARY OF CURRENT RESEARCHES RELATING TO 



their structure, and concludes tliat they are respiratory in function. 

 There are no glandular tubes or acini, and no excretory ducts. In both 

 adult and embryo the tissue is that of a mesodermic vascular organ. 



Structure of Mantle of Calyculina (Cyclas) lacustris, Mtiller.* — 

 0. Schroder describes the histological structure of the mantle of Gahj- 

 culina. The most interesting feature consists of slender threads which 

 are seen in decalcified examples to stretch from the mantle epithelium 

 to the periostracum across the space left by the decalcified shell. These 

 threads clearly correspond to the small canals of the shell. They are 

 prolongations of certain cells of the mantle epithelium. They are 3/x 

 thick and in thickest parts of shell may be 61V long. Externally they 

 are enveloped by the same organic membrane which the nacre leaves 

 behind on decalcification. Internally there is a delicate fibre, which is 

 traceable basalwards to the nucleus of the cell. 



Determination of Sex.f — F. H. Pike communicates a critical and 

 statistical study on the determination of sex, with special reference to 

 human offspring. In man there is a slight but constant excess of male 

 births ; the greater mortality of the males leads to a preponderance of 

 females in old age. The proportion of the sexes is remarkably constant 

 in widely different localities and times. The study of duplicate twins 

 shows that if sex is determined by a series of accidental causes, such 

 causes cannot be operative after the fertilisation and first segmentation 

 of the ovum. " The logical conclusion from the statistical data is that 

 sex is hereditary. Mendel's law does not apply. The constancy of the 

 sexual ratio for more than two hundred years may best be explained by 

 supposing that sex follows Galton's law of ancestral inheritance. If sex 

 is hereditary, we may explain the significance of the sexual ratio on the 

 basis of natural selection by supposing that the proportion of the sexes 

 in any species is such as will give that species the maximum reproductive 

 power at the time of sexual maturity of its individual members. The 

 sexual proportion may be considered as one of the physiological adapta- 

 tions of a species." 



Spontaneous Generation.! — M. Kuckuck finds that it is not very^ 

 difficult to make little hving creatures. Take a mixture of gelatin, 

 pepton, asparagin, glycerin, and sea-water ; sterilise it by boiling for an: 

 hour ; put it in a sterilised vessel ; and add a little chloride of barium. 

 This brings about ionisation, and ionisation leads to organisation. 

 Kuckuck thus obtained minute protist-like bodies, which feed and grow 

 and rotate and form cell-colonies like morulte. The drawings of these 

 are indistinguishable from drawings of morula, and each cell has a 

 very distinct nucleus. Some photographs are also submitted. Similar 

 bodies were obtained from fresh albumin and from yolk of egg by using 

 barium chloride as an ioniser. Drops of "natrium nucleinicum" (Merck) 

 allowed to fall on the surface of the gelatin mixture produce rotating 

 corpuscles, which form loose colonies. Kuckuck argues from his experi-- 



* Zool. Anzeig., xxsi. (1907) pp. 506-10 (2 figs.). 



t Amer. Naturalist, xli. (1907) pp. 303-19. 



X Die Losuug des Problems der Urzeugung. Leipzig (1907) 83 pp., 34 figs. 



