BEPEODUCTIVE ELEMENTS IN APUS AND BEANCHIPUS. 259 



Some Points in the Origin of the Reproductive 

 Elements in Apus and Branchipus. 



By 



J. E. S. Moore, A.R.C.S., 



From the Huxley Research Laboratory, Royal College of Science, London. 



With Plates 15 and 16. 



The mode of generation of the reproductive elements and 

 their relation to the cells of the parental tissues, is a problem 

 which has always made heavy demands on the labours of micro- 

 scopical investigators, whether zoological or botanical ; and 

 although an immense literature has grown about the subject 

 since Elourens thought embryos were, formed "tout d'un 

 coup," at the moment of the fusion of the sexual elements, it 

 may be safely asserted that not until the last few years has any 

 very definite knowledge been acquired, and only in a limited 

 number of cases has it yet reached any high degree of accuracy. 



In a certain number, however, we do know what is actually 

 done during the origin of these cells ; and this knowledge is a 

 priceless gift to the biologist, as there is little doubt that the 

 apprehension of karyokinesis, both in its relation to the 

 " Reductions-Theilung " and the ordinary division of somatic 

 cells, has brought him face to face with the actual mechanical 

 expression of hereditary transmission and the problems con- 

 nected with it. 



The modus operandi of the forces which bring about these 

 changes, however, or any serious attempt to ascertain whether 

 they be modifications of ordinary physical phenomena at all, 

 or whether the whole "fleeting show " of attractions, repulsions, 

 and nuclear metamorphoses must be looked upon as something 



