ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 29 



Q 



that the cliaracteristic cells of the corpus luteum are formed by hyper- 

 trophy of the cells of the membrana granulosa. The theca interna 

 folliculi is rudimentary, and forms only the vascular connective tissue of 

 the corpus luteum. The corpus luteum is probably a gland with an 

 internal secretion of use in the organism. It has the function of stopping 

 ovulation during pregnancy, and at the cestral periods. 



Problem of Form Regulation.*— S. J. Holmes propounds a theory 

 according to which the process of form regulation does not necessarily 

 involve the preservation of favourable variations among the vital units, 

 although it may involve one factor of that process, viz. the tendency of 

 parts to increase as fast as circumstances permit. He conceives that the 

 checking process by which regulation is effected, is brought about not by 

 the selection of certain vital units, but through the symbiotic relation in 

 which the parts of the organism stand. The whole process of develop- 

 ment may occur without the elimination of vital units of any kind, 

 whether they be biophors, determinants, or individualities of a higher 

 order, such as cells or organs. The parts of an organism are engaged in 

 a struggle for existence, but as the parts are mutually dependent, the 

 struggle leads to an adjustment to a norm instead of the elimination of 

 some parts and the survival of others. 



Regeneration of Bone and Cartilage.! — Wendelstadt has made 

 numerous experiments on newts and axolotls. When there is regenera- 

 tion of bony tissue, there must be a return to the primitive cell-forms. 

 The bony tissue itself cannot form new bone nor cartilage. There must 

 be a re-habilitation of those elements which were active in embryonic 

 life, and these are retained in the periosteum. They form, first, cartilage 

 cells, and then these are transformed into osseous elements. 



Development of the Sense Organs of the lateral line in Am- 

 phibia.}: — R. G-. Harrison finds experimentally that the path of the 

 lateral line organs may be varied, and that the path characteristic of a 

 particular species is merely to be considered as the line of least resist- 

 ance to growth. The stage of development used in the experiments was 

 that when the tail bud just appears, and at this stage the causes con- 

 ditioning that certain cells belong to the lateral line appear to have been 

 active at an earlier period of development. 



Development of Lymph Glands in Man.§ — C. A. Kling, in a series 

 of studies of human embryos, has made out, amongst others, the follow- 

 ing points. The axillary lymph vessels have developed an abundant 

 plexus before the gland proper arises. In the third foetal month, in the 

 meshes of the lymph-vessel plexus cellular and vascular tissue is differ- 

 entiated, showing an irregular trabecular arrangement. Such an area 

 corresponds to each of the gland groups in the axilla, and may be termed 

 lymph-gland centres of origin. Through division of these are formed 

 the single glands. The division appears to be caused by the ingrowth 

 and dilatation of the neighbouring lymph vessels. Lymph sinuses in the 



* Arch. F.ntwickelurigsmecl]., xvii. (1903) pp. 265-305. 

 t Arch. Mikr. Anat., Ixiii. (1004) pp. 766-95 (6 pis.). 

 X Turn, cit., pp. 35-119 (3 pk.). 

 § Op. cit., Ixiii. (1903) pp. 575-G10 (2 pis). 



