294 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the vitelline capsule, which includes (l)an internal layer, the vitelline 

 membrane of the ovarian ovum ; (2) a median layer, the remains of the 

 granulosa of the ovarian follicle ; and (8) an external layer, the most 

 internal part of the theca of the ovarian follicle. 



Polynuclear Ovum in Bat.* — A. Guieysse-Pellissier describes in 

 Vesperucjo abramus a strange kind of abortive ovum, which has become 

 polynuclear through the immigration of adjacent cells derived from the 

 granulosa and of leucocytes. 



Double Egg in Porbeagle Shark. f A. Vayssiere describes a double 

 egg in the left oviduct of Lamna cor/iubica. The separate developing ova 

 were enclosed in a single shell, which was too large to be expelled. 



Egg of Rhinophis4 — L. Baumeister describes the egg and embryo 

 in Rhinophis trevelyanus. The number of eggs that develop at one 

 time is reduced to two (in adaptation to subterranean life and viviparous 

 birth at an advanced stage) ; they occur only in the left oviduct ; the 

 egg-envelopes are extremely delicate and without calcareous encrustation ; 

 the shape of the eggs is an elongated cylinder. 



Mitochondrial Elements of Germ-cells and Chondriosomes of 

 Embryonic Cells.§ — J. Duesberg has succeeded in the rabbit in demon- 

 strating the continuity of the mitochondrial elements of the ovum and 

 the chondriosomes of the somatic cells of the young embryo, thus show- 

 ing the maternal origin of at least some of them. 



Development of Autonomic Nervous Mechanism of Birds' Alimen- 

 tary Canal. ||--Williamina Abel finds that the whole sympathetic system 

 is secondary in formation to, and directly derived from, the central 

 nervous system. The abdominal sympathetic is produced by the migra- 

 tion of cells from the spinal cord and intervertebral ganglia downwards 

 through the mesentery to the gut. From these cells are formed the 

 various divisions and synapses of the autonomic system. That these 

 cells are not the sheath-cells described by Harrison as growing from the 

 posterior root in the tadpole is indicated by some of their number sub- 

 sequently forming the cells from which the two plexuses in the intestinal 

 wall develop. 



Development of Lymphatic Ganglia of Duck. If — J. Jolly finds that, 

 while the typical lymphatic ganglia of Mammals are formed by the 

 growth of a mesenchymatous nodule between the lymphatics crowded 

 at the periphery and forming the marginal sinus, those of the duck 

 develop by the progressive partitioning of a lymphatic vessel, mesen- 

 chymatous buds growing in on the cavity at short intervals. Associated 

 with this, there is an invasion of adjacent adipose lobules by the lym- 

 phoid tissue, an extension of the spongy substance and of the sinus net- 

 work by accessory lymphatics and by budding of sinuses. 



* C.R. Soc. Biol. Paris, lxvii. (1909) pp. 692-4. t Tom. cit., pp. 872-3. 



X Zool. Jakrb.,xxviii. (1910) pp. 603-10 (6 figs.). 

 § Anat. Anzeig., xxxv. (1910) pp. 548-53 (4 figs.). 

 I, Prcc. Roy. Soc. Edinburgh, xxx., pp. 327-47 (4 pis.) 

 1 C.R. Soc. Biol. Paris, lxvii. (1909) pp. 684-6. 



