172 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in water up to 40° C, between 40° and 45° the number of species de- 

 creases, wbile the number of individuals increases. Even in water of 

 54*5° he found Pelomyxa villosa thriving. 



Issel recognises five categories : — (1) widely distributed forms 

 common in cold water, e.g. Philodina roseola and Ghilodon cucullus ; 

 (2) animals which ascend periodically from the sea (Anguilla vulgaris), 

 or which have recently immigrated into fresh water {Palsemonetes 

 varians) ; (3) forms which are at home in the warm water, but absent 

 in the surrounding basins (e.g. Hydroscaj)ha gyrinoides) ; (4) forms now 

 restricted to the thermal waters, but found elsewhere as fossils {Mela- 

 nosis etrusca); (5) typical inhabitants of hot mineral springs (Lacobius 

 sellm). In his second paper the author discusses in particular the 

 differences between thermal forms and their relatives elsewhere. 



Okapia johnstoni.* — Prof. E. Bay Lankester points out the general 

 resemblance in skull and dentition between this new mammal from 

 Central Africa and the giraffe. Both he and Gaudry f corroborate the 

 suggestion of the discoverer, Sir Harry Johnston, that Okapia is gene- 

 tically related to the extinct Helladotherium. 



"Chestnuts" of Horse.J — E. E. Beddard suggests that these may be 

 profitably compared with the tactile (?) carpal tufts of vibrissa? which 

 he has observed in numerous mammals, which Bland Sutton first noted 

 in Lemuroids. In Dasypus villosus the carpal tuft of vibrissas is present, 

 but instead of being a closely compacted tuft of about six hairs, as is 

 usually the case, the hairs in the armadillo are not much larger than 

 those cf the skin generally, are spread over a thickened patch of skin 

 about half an inch in length, and are more numerous. In Lemur catta 

 there is a callous tract of skin close to which is a tuft of vibrissa?. If 

 the latter were lost we should have the "chestnut" of the horse, which, 

 on the fore-limb, occupies '• the right position," a little above the wrist. 



Modifications in Alimentary System of Birds induced by Diet.§ — 

 F. Houssay refers to previous experiments on this subject (Hunter, 

 Edmonstone, Semper, Holmgren, and Brandes), and gives a careful 

 account of his own, which relate to two similar sets of fowls (three in 

 each set). The members of the one set were fed on grain, the others on 

 flesh. Precise measurements are given. In those fed on flesh the crop 

 was much shorter and smaller; the intestine and caeca were also much 

 reduced in dimensions ; there was also a considerable reduction in the 

 weight of the gizzard. But there is need for a larger number of data. 



Vascularisation of Intestine in Vertebrates. || — Henri Neuville has 

 studied the vessels of the alimentary caual in Cyclostomes and Elasmo- 

 branchs, in order to compare the physiology of absorption in the higher 

 and lower Vertebrates. His results show that, as might have been ex- 

 pected, the higher show considerable division of labour as compared 

 \\ ith the lower. Neither in the lamprey nor in Elasmobranchs is there 

 any trace of the complicated chyliferous system of mammals. In both 

 cases the vessels of the intestine are either arteries or veins, no lymph- 



* Comptes Rendus, exxxiii. (1901) pp. 857-8. 



+ Tom. cit., pp. 858-9 (appended note). % Nature, lxv. (1902) p. 222. 



§ Comptes Rendus, exxxiii. (1901) pp. 1022-5. 



|| Ann. Bci. Nat. Zool., xiii. (1901) pp. 1-116 (2 pis. and 22 figs.). 



