286 SUMMARY OF CURRENT RESEARCHES RELATING TO 



equation division. The phenomena observed in Tomopteris ai-e regarded 

 as fundamentally typical of the chromosome maturation of sex cells in 

 both animals and plants in general. 



On Heterochromosomes.* — S. Gutherz gives an account of the 

 various types of heterochromosomes referred to in recent literature, with 

 a particular description of those occurring in the sex cells in GryUus 

 domesticus and Pyrrhocoris apUriis. In the former, in spermatogenesis, 

 there is a heterochromosome of the monosome type with heterokinesis I, 

 which in the sperm ogonia is distinguished from the twenty usual 

 chromosomes by its special size and shape. In the male somatic mitosis 

 there occurs no such element. In the first maturation mitosis the half 

 spindle fibres attach to the ordinary chromosomes ; the monosome 

 undergoing heterokinesis receives no such fibres. 



Interstitial Gland of Ovary.f — J. Bergonie and L. Tribondeau 

 find that under the X-rays the ovary of the rabbit undergoes a 

 diminution of volume. This is due to the atrophy of the interstitial 

 gland, whose constituent nodules become separated, and whose cellular 

 elements undergo shrinkage. 



Action of Corpus Luteum Extract.^ — Lambert has submitted frogs 

 and rabbits to various injections of corpus luteum extract of the sow 

 and cow, with highly toxic results. There is a clear analogy between 

 the action of extracts of glands of internal secretion and those of the 

 corpus luteum : the latter, however, exhibits the highest toxicity of all. 



Experimental Degeneration of Seminal Gland in Mammals. § — 

 P Ancel and F. Villemin find that ablation of the parietal layer of the 

 vaginale results in the degeneration of the seminal gland, whilst the 

 morphological and functional integrity of the interstitial gland is 

 undisturbed. 



Tooth-development in Ornithorhynchus. || — J. T. Wilson and 

 J. P. Hill have studied two specimens of mammary foetus of the 

 duckmole. The facts set forth seem to establish the existence of teeth 

 belonging to at least two dentitional series. In the series to which the 

 multicuspidate teeth of the adolescent animal belong there are probably 

 five members. Besides these there seems to be a " nodular series — 

 vestigial deciduous predecessors of the large molar teeth, much simpler 

 in nature, each on the whole corresponding with one of the cusps of their 

 multicuspidate molariform successors. But the early differentiation of 

 nodules is not entirely confined to the region to be occupied by molar 

 cusps. The relation of the two series in the molar region cannot but be 

 regarded as suggestive of some sort of phylogenetic substitution of a 

 small number of compound teeth for a large number of simple teeth — a 

 process which must be reckoned as covering the fundamental idea of 

 concrescence. 



* Arch. Mikr. Anat., Ixix. (1907) pp. 491-514 (12 figs.). 

 t C.R. Soc. Biol. Paris, Ixii. (1907) pp. 274-7, 

 % Tom. cit., pp. 18-20. § Tom. cit., pp. 6-8. 



|l Quart. Journ. Micr. Sci., li. (1907) pp. 137-65 (3 pis.). 



