572 SUMMARY OF CURRENT RESEARCHES RELATING TO 



In another paper * the author discusses the structure of the brain of 

 Mus, with some observations on that of Echidna, and in regard to the 

 phylogen y of the brain of Vertebrates comes to the following conclusions. 

 The primitive basal part of the brain in Selachians underwent in the 

 ancestors of Reptiles a differentiation into a median and a lateral half, 

 which became attached respectively to the median and lateral parts of 

 the pallium, and formed the primary gyrus fornicatus and the striatum. 

 A further differentiation of the lateral region produced the epistriatum. 

 An invagination and differentiation of the pallium above the primary 

 gyrus fornicatus produced a reptilian condition of parts, the differen- 

 tiated pallium having olfactory significance. A farther specialisation of 

 the olfactory sense produced the gyrus ammonis which grows downward 

 over the primary gyrus fornicatus, so that the basal olfactory region of 

 the brain contains a purely pallial element. At the same time the non- 

 olfactory region of the pallium underwent further differentiation. The 

 development of the superior commissure — a connection between the gyri 

 ammonis of the two sides — produced the Monotreme condition. Then 

 the anterior part of the gyrus ammonis underwent degeneration, while 

 simultaneously the non-olfactory region of the pallium and its system of 

 cross fibres underwent further development. This system of cross 

 fibres becomes differentiated from the large inferior anterior commissure 

 of Monotiemes, which gradually diminishes in importance. As the 

 cortex of the brain increases in importance and the number of asso- 

 ciation centres becomes greater, a strong system of transverse fibres 

 appears, and forms the corpus callosum. The result of this is the 

 development nf the true gyrus fornicatus, which becomes differentiated 

 out of the primary gyrus fornicatus, and replaces the anterior part of the 

 gyrus ammonis, while its posterior part becomes degenerate. Thus the 

 gyrus fornicatus cannot be included as part of the rhineccephalon. 

 The importance of the corpus callosum is that it contains crossed 

 association tracts, which, when combined with association centres, mean 

 increased intelligence. In Echidna there is a differentiation of the 

 cortex without any great increase of intelligence, and here the crossed 

 association tracts are not numerous. 



Sensory Canals of Polypterus bichir.f — Mr. E. P. Allis, jun., finds 

 that the lateral canals of this fish present a condition that represents a 

 perfectly normal development, excepting only in the fusion, in one 

 specimen, of the fifth and sixth primary pores of the mandibular line to 

 form a single pore. No primary pore in the entire lateral system of the 

 fish has undergone secondary subdivision, Polypterus presenting in this 

 a much lower stage of development than either Amia or Lepidosteus. 

 The author describes the mandibular canals (which unite at the symphy- 

 sis), the main infra-orbital canals (which unite on the top of the snout), 

 the supra-orbital canal, the supra-temporal commissure, the pre-opercular 

 canal, the pit-organs, and the three sensory lines on the body of the 

 fish, the more important one having the most ventral position, and 

 corresponding, apparently, to the main lateral line of other fishes. 



Kidney of Lepadogaster gouanii.J — M. Frederic Guitel fiuds that 

 in the male of this fish the kidney consists of a posterior lobed region, 



* Morph. Jahrb., xxviii. (1900) pp. 347-477 (7 pis. and 4 figs.), 

 t Anat. Anzeig., xvii. (1900) pp. 433-51 (3 rigs.). 

 \ Comptes Kendus, cxxx. (1900) pp. 1773-7 (2 figs.). 



