226 The Irish Naticj-alist, November, 



Stevens, through which Professor E- B. Wilson, herself, and 

 other American cytologists have demonstrated the presence 

 of an odd number of chromosomes (one less than the normal 

 number) in some spermatozoa of certain species of insects, 

 these spermatozoa apparently fertilizing female-bearing eggs, 

 those with the full number male-bearing eggs. Professor 

 Bateson also supported the theory' from breeding experiments 

 with Canary Finches. Mr. Heape, on the other hand, gave 

 reasons — derived for the most part from human birth-statistics 

 — in support of somatic influence on the determination of sex. 



Kvolutionar}' problems of an older and simpler type were 

 raised on Thursday, 3rd, by Professor Poulton, Dr, F. A. 

 Dixe}', and Mr. J. C. Moulton, who exhibited and discu.ssed 

 series of butterflies, illustrating "convergent mimicry" of 

 distasteful forms. Embryologists were well pleased to 

 w^elcome Professor A. W. Hubrecht as a vice-president ; he 

 took the chair on Monda}' afternoon, September 7th, when 

 Professor J. P. Hill described the " Segmentation of the 

 Marsupial Ovum," and Professor E. W. MacBride "Gastrul- 

 ation in Amphioxus." These two authors defended respec- 

 tively the ancestral value of the monotreme yolked ^zz, and 

 the ectodermal nature of all the inpushed cells in the Amphi- 

 oxus gastrula. Both of these familiar positions were genially 

 attacked by the great Dutch embryologist. Later in the same 

 afternoon, Dr. A. Smith Woodward, F.R.S., of the British 

 Museum, delighted the Section with a lecture on the "Evo- 

 lution of Fishes." On Friday afternoon (4tli Sept.), Professor 

 Cossar Ewart lectured on the " Wild Ancestors of the 

 Domestic Horse," expressing his belief that the North-western 

 and Libyan races of domestic horses are both derived from 

 Equus gracilis of the French Pleistocene. 



Geographical zoology was represented by Dr W. A. Cun- 

 nington, who described his recent expedition to Lake Qurun, 

 in Upper Egypt; of very special interest were the announce- 

 ments of a freshwater gymnolsematous polyzoon with a 

 circular lophophore and eight tentacles, and of a freshwater 

 medusa with its hj^droid stage. Professor W. A. Herdman 

 contributed " Notes on a recent visit to the Ceylon Pearl 

 Bank," and Professor G. H. Carpenter gave an account of 

 newly-discovered Arctic and Antarctic Collembola, 



