ZOOLOGY AMU BOTANY, MICROSCOPY, KTC. 25 



reduction of the alimentary canal, furnish a large amount of absorbed 

 material, and this perhaps hastens the definitive development of the limbs 

 and the formation of the spiracular opening. 



Experiments with Axolotls.* — P. Wintrebert describes his method 

 of transforming axolotls into amblystomas in an inclined aquarium with 

 an aquatic portion and a relatively dry portion, and with some sponges 

 forming an intermediate area. He tried Powers' method of leaving the 

 axolotls in the water, and suddenly stopping the food supply after a 

 period of super-abundant nutrition. But no transformation was effected 

 in this way. A modification of Marie von Chauvin's method, as above 

 suggested, is usually effective. The importance of the environmental 

 factor has been exaggerated ; the hereditary influence is paramount. 



Segments of Head and Brain in Gull.f — A. Meek has studied 

 embryos of the Lesser Blackbacked Gull (Larus fuscus). He dis- 

 tinguishes in the prosencephalon three regions or " prosomeres," in the 

 mesencephalon two regions or " mesomeres," and in the rhombencephalon 

 thirteen " rhombomeres." Seven head somites are clearly represented 

 in the gull, but the author finds reasons for concluding that the total 

 number of segments -was lbh. The probable relation of these to the 

 ganglia is indicated. According to the author, the mixed dorsal nerves 

 " were primarily, and are still, largely developed from a series of inter- 

 segmental ectodermal ganglia, and the connection with the brain and 

 spinal cord is a secondary one. The ganglia became connected together 

 by longitudinal commissures forming a chain of ganglia on each side, 

 and extending to a common meeting place in front of the brain — at all 

 events, in the Cyclostomes. Those in the body lost their connection 

 with the spinal cord, but retained their relationship with the ectoderm, 

 thus forming the nerve and organs of the lateral line." " In the head 

 region the ganglia and the nerves arising from them attained a con- 

 spicuous development, establishing the organs of sense, the sensory, and, 

 with few exceptions, the motor nervous system of the region, and 

 extending in certain cases beyond it.' 1 The author sees reasons for 

 concluding that " an early transitory attempt at a lateral line formation 

 takes place in the gull, in other birds, reptiles, and mammals." 



Development of the Alimentary Canal in the Trout. i- — Sophie 

 Egounoff describes the development of the various regions of the trout's 

 alimentary canal. The oesophagus arises from a solid endodermic tract, 

 surrounded by a mesodermic sheath ; its anterior and posterior regions 

 develop differently. The stomach is also solid to start with. In both 

 oesophagus and gullet, the connective tissue, the circular muscles, the 

 longitudinal muscles develop in the order in wbich these are named. 

 The intestine becomes hollow first, and remains long in the form of a 

 cylindrical tube lined by simple cylindrical epithelium. After the 

 intestine has assumed its definitive structure, the pyloric appendages arise 

 by the evagination of the wall. 



* C.R Soc. Biol. Paris, lxiii. (1907) pp. 521 3. 

 + Anat. Anzeig., xxxi. (1907) pp. 408-15 (5 figs.). 

 J Rev. Suisse Zool., xv. (1907) pp. 19-74 (2 pis.). 



