104 Prof. J. B. Farmer and Mr. J. E. S. Moore. [May 29, 



New Investigations into the Reduction Phenomena of Animals 

 and Plants. Preliminary Communication." By J. B. FARMER, 

 F.R.S., and J. E. S. MOORE, A.R.C.S. Received May 29, 

 Read June 18, 1903. 



The attention given by numerous investigators to those periodically 

 recurring nuclear changes known as reduction divisions, has so far 

 apparently resulted only in an increasingly wide divergence of opinion, 

 both respecting the nature of the process and its significance, but there 

 are nevertheless a number of cardinal facts upon which all are fairly 

 agreed. It is generally admitted, for example, that during the 

 reduction processes the number of the chromosomes is halved ; that 

 this is everywhere effected during the period of rest immediately pro- 

 ceeding the mitoses in question ; that two consecutive mitoses appear 

 to be intimately connected with this process, but the first of these, the 

 heterotype division, is generally markedly distinct from other nuclear 

 divisions ; consequently it would seem probable that the explanation of 

 the reduction in the number of the chromosomes, of reduction generally, 

 is to be obtained through a minute study of the heterotype or synaptic 

 prophase in a large number of animals and plants. With this concep- 

 tion before us, we have sought out in each case as complete and 

 unbroken a series as possible, illustrating the stages by which the 

 synaptic spireme thread is converted into the reduced heterotype 

 chromosomes ; and the results of our investigations have not only been 

 such as to considerably modify the conception of the process as already 

 set forth by ourselves in a number of former memoirs, but at the same 

 time to indicate a possible reconciliation between most of the different 

 views which have been and are held by other investigators. 



The two main theories as to the nature of reduction may be shortly 

 stated. In the first we have the process regarded as a qualitative and 

 quantitative division of the chromatin by the ultimate separation 

 into daughter nuclei of entire somatic chromosomes. It is assumed 

 that such entire chromosomes may be temporarily united during the 

 early prophase of the heterotype division, and thus a " pseudo-reduc- 

 tion " (Hacker) be brought about. But during the homotype division 

 these chromosomes are separated and pass in their entirety to one or 

 other of the daughter nuclei. It is held by most investigators that the 

 final separation is effected during the second or homotype division, the 

 heterotype being characterised by the separation of the longitudinally 

 split halves of the chromatic thread-work. 



The second view is that which was strongly urged by Brauer, and is 

 now held by a large number of both zoological and botanical investiga- 

 tors. According to this conception the identity of the original somatic 



