634 SUMMARY OF CURRENT RESEARCHES RELATING TO 



inconsistent with what Weismaun has maintained in regard to its 

 adaptive significance. 



Branchial Clefts in Lizard and Slow-worm.* — Prenant and Saint- 

 Remy corroborate on the whole the conclusions of Maurer. 



The first cleft does not develop as such, but is at its first appearance 

 a dorsal sensory organ ; the second cleft gives rise to the anterior 

 thymus; the third is associated with the posterior thymus and a para- 

 thymia glandule ; the fourth gives rise to a structure like a parathymic 

 glandule, but this degenerates completely ; the fifth, developed in 

 Lacerta, is quite transitory in the slow-worm. There is a paired post- 

 branchial evagination, but that on the left retrogresses and usually dis- 

 appears, while that on the right becomes a gland which is at its maximum 

 in young forms, and retrogressive in adults. 



Skull and Nervous System of Ceratodus.f — A. N. Sewertzoff has 

 studied the development of the primordial cranium of Ceratodus and 

 the nervous system. In its development the cranium of this Dipnoan 

 shows a greater resemblance to that of Urodela than to that of any 

 other group. On the other hand, there are not a few distinctive features 

 which do not occur in Amphibia. Moreover, as one would expect, the 

 resemblance to Amphibia decreases as development proceeds. 



The distribution of the nerves in Ceratodus is in general the same 

 as in Protopterus, as described by Pincus, while some peculiarities, e.g. 

 as to the nervus praaopticus, distinguish it sharply from that of other 

 Vertebrata. 



Structural Feature connected with Mating of Diemyctylus viri- 

 descens.| — W. A. Hilton describes the quaint mating habits in this 

 Urodele. After excitation, in which the male touches the female with 

 the sides of his head, the male leaves the female but is closely followed 

 by her. The male moves slowly forward and throws his body into 

 serpentine undulations, and a spermatophore is emitted which may 

 come to the cloaca of the female as she follows her mate farther along. 

 "What is the nature of the attraction which leads the female to follow ? 



Hilton's suggestion is that it may be in part due to the secretion of 

 three or four quite large, deep glandular pits which extend from the 

 back of the male's eye along the side of the head. They are repre- 

 sented by small pin-prick-like minute depressions in the female. Adult 

 males taken at any time except the breeding season show the gland 

 tubules associated with the pits in a resting state ; when breeding the 

 gland lumens are filled with secretion. No pits or glands were found 

 in D. torosus, whose breeding habits are dissimilar. 



Palaeontology and Evolution.§ — E. Koken expounds a number of 

 conclusions which command general assent. The palaeontologist has to 

 deal with the most direct " evidences of evolution," — there are fossil- 

 series, there are extinct links between modern types, there is an un- 

 mistakable progress, and so on. 



* Comptes Itendus, cxxxv. (1902) pp. 62-3. 

 t Anat. Anzeig., xxi. (1902) pp. 593-608 (5 figs.). 

 X Amer. Nat, xxxvi. (1902) pp. 643-51 (11 figs.). 



§ ' Palaontologie und Descendenzlehre,' Jena, 1902, Svo, 33 pp. See Zool. Cen- 

 ■ tralbl., ix. (1902) pp. 432-5. 



