42 The Ohio Naturalist. [Vol. VII, No. 3, 



similar contractions in other reduction cells, as microsporocytes 

 and megasporocytes, or any other cells, in which a similar phe- 

 nomenon is observed. Accepting this terminology as conducive 

 to lucidity of expression, synapsis will then normalh' mean the 

 process by which two univalent chromosomes become united to 

 form one bivalent chromosome ; or, in case a continuous spirein is 

 formed by the end to end conjugation of univalent chromosomes, 

 the process by w^hich two univalent chromosomes become so 

 united that at the time of the transverse segmentation of the 

 continuous spirem they do not break apart as in previous divi- 

 sions but are brought into the mother star as single bivalent 

 pieces. 



This will then include the idea expressed by the term, pseu- 

 do-reduction, which refers only to the fact that half as many 

 chromatin pieces are present as in the previous division. Syn- 

 apsis must not be confounded with the fusion of chromosomes in 

 the network during each resting period nor with the ordinary 

 fusion by which a continuous spirem is produced. 



Recenth' the writer has studied a considerable number of 

 preparations in order to refresh his mind upon this subject. The 

 few figures presented are given merely as examples of a very 

 large number of distinct types of chromatin contraction, which 

 may be observed. 



Some confusion has been produced by the use of the terms 

 longitudinal and transverse division. Evidently it is of no im- 

 portance whether two entire univalent chromosomes conjugate 

 to form a ring, a twisted loop, or a simple longitudinally united 

 or folded pair, so long as they separate during metakinesis. 

 Transverse division means a qualitative division, longitudinal 

 division a quantitative division. In such bivalent chromosomes 

 as occur in the megasporocytes of Lilium philadelphicum (tig. 1), 

 and Erythroniuni albidum and americanmn, and in the micro- 

 sporocytes of Liliufn tigrinum the two limbs of the chromosomes 

 lie folded on each other and twisted together. But the real 

 reduction division is not so much the pulling apart of the two limbs 

 but the transverse break in the loop at the head of the chro- 

 mosome which is supposed to represent the point of the synaptic 

 fusion of the pair of uni^•alent maternal and paternal chromo- 

 somes. 



Synapsis and reduction then are simply processes by means 

 of which entire chromosomes, presumably maternal and paternal, 

 are segregated into the daughter nuclei ; or by which at least qual- 

 itative division of the chromatin is accomplished in case there is 

 a mixing of paternal and maternal chromatin during the "2.v" 

 phase of the organism. The whole process appears to be merely 

 a mechanical contrivance for bringing about qualitative separa- 

 tion. We may consider chromosome reduction as a necessary 



