Germ Cells of Leptinotarsa Signaticollis. 189 



the behavior of the two halves of the spireme is such as to indi- 

 cate two more or less independent parts, as in Figs. 39 and 42, 

 where the halves are widely separated, and Fig. 50, where the 

 separation is partial. These facts, together with the relation of 

 the segments of the spireme to the presumably bivalent nucleolus, 

 point to a separate origin of the two components of the spireme, 

 as opposed to their resulting from a longitudinal splitting of a 

 single series of units united end to end. 



On this basis the synaptic process would take place somewhat 

 as follows: In the post-telophase stages of the last pre-matu- 

 ration division, the chromosomes arrange themselves side by side 

 in homologous pairs to form a long thin double spireme behind 

 the accessory body, which arises from two chromosomes that, 

 instead of elongating as the rest of them do, contract to form the 

 nucleolus of the resting stage. The line of separation between the 

 two homologous series indicates one of the m.aturation divisions. 

 The other division (except in the case of the nucleolus which only 

 divides once) is indicated by a tranverse groove in each chro- 

 mosome which produces the large number of segments seen in 

 synizesis and stages immediately after (Figs. 39 to 47 inclusive). 

 With the exception of the nucleolus, all trace of chromosome struc- 

 ture is lost during the resting stage. The first indication of a 

 reconstructing process is shown in Fig. 49 by the appearance of 

 two parallel strands upon which the chromosomes take their 

 places as shown in Figs. 50 and 51. 



The occurrence of side to side union of the chromosomes or 

 parasynapsis (Wilson '09a), has a bearing on certain theoretical 

 aspects of maturation. It can be readily shown that the two 

 divisions take place at right angles to each other (Figs. 53 to 60 

 inclusive). Thus in one division whole chromosomes are separ- 

 ated and in the other, each of these is divided transversely. 

 Therefore no equational division occurs; and this to some would 

 be a fatal objection to parasynapsis as outlined above. Before 

 such an objection can be taken seriously it must first be shown 

 that the supposed difference between ''quantitative" and" quali- 

 tative " divisions really exists. The theory rests upon the assump- 

 tion of the arrangement of the chromomeres of each chromosome 



