30 SUMMARY OF CURRENT RESEARCHES RELATING TO 



authors refer especially to nodular tuberculiform growths (pseudo- 

 tuberculosis), apparently occurring apart from bacterial infection. 



Embryological Methods.* — Sandor Kaestner discusses in an intro- 

 ductory lecture the history of embryology, and emphasises the transition 

 from a morphological to an experimental basis. Modern regeneration- 

 experiments and teratogenetic experiments represent the high-water 

 mark. The recapitulation-doctrine was a powerful impulse for a time, 

 but the conception of Entwicklungsmechanih, so prominently associated 

 with the work of Roux, is now dominant. 



b. Histolog-y. 



Brain of Mustelus.f — Prof. G. H. Houser has made a detailed study 

 of the structure of the brain in this Selachian, with particular reference 

 to the neurones and supporting elements. We must restrict ourselves 

 to noticing his most general conclusion. There is a most remarkable 

 structural similarity between the brain of Mustelus and the brains of 

 higher vertebrates. The neurones are, of course, simpler in their external 

 structure, and their architectural relations are of a far less complicated 

 order, yet it is none the less true that they anticipate the conditions 

 found in higher vertebrates in all important particulars. The fact can 

 only be interpreted to mean that the nervous system of the primitive 

 vertebrate had its essentials of organisation well denned before the 

 divergence of the several phyla occurred. 



The cerebellum is far more highly differentiated than that of am- 

 phibian or reptile ; the medulla oblongata, on the contrary, has retained 

 the plan of structure of the primitive neural tube without the inter- 

 vention of profound changes ; a more extreme degree of simplicity is 

 found in the inter-brain or thalamencephalon ; the fore-brain is far in 

 advance of that of teleosts or ganoids. 



These illustrations point to an underlying principle. The organi- 

 sation of the brain is the expression of the adjustment which has con- 

 stantly taken place between the race of animals and the stimuli to which 

 they have been subjected. Hence it is that the cerebellum of Mustelus 

 is so highly organised ; for this is the correlative of the powerful 

 swimming capacity of the animal, requiring an adequate mechanism of 

 equ libration. The fore-brain, with its luxurious development of 

 neurones, has arisen in connection with the large place occupied by 

 olfactory impressions in the Selachii. 



Skin-Glands of Amphibians.^ — Dr. P. Ancel shows that these glands 

 have an ectodermic origin. The pi'imordium, arising from the cells of 

 the deep layer of the epidermis, protrudes into the dermis, and comes to 

 be surrounded by it except at the upper pole. The excretory canal is 

 formed from a depression of the stratum corneum between several epi- 

 dermic cells. As to the " collar," it is formed secondarily at the union 

 of ti»e epidermis and glandular bud, and is from the very first dis- 

 tinguishable into an internal and external portion. Precisely the same 



* Embryologische Forschungsmethoden. Antrittsvorlesung, Leipzig, 1900. 30 pp. 

 See Biol. Centralbl., xxi. (1901) p. 683. 



t Journ. Comp. Neurol., xi. (1901) pp. 65-175 (8 pis.). 

 t Arch. Biol., xviii. (1901) pp. 257-89 (2 pis.). 



