ORTHOPTERAN SPERMATOGENESIS 697 



first spermatocyte may be entirely new structures, having no 

 relation either in material or in form to those of the spermato- 

 gonium, (b) they may be derived in substance only from the 

 spermatogonial elements, or (c) they may individually be de- 

 scended from similar structures without loss of identity other 

 than that involved in the processes of chromatin metabolism. 

 All these conceptions have found expression in studies on Orthop- 

 teran material. 



Granata ('10), adopting the views of Giglio-Tos, argues for a 

 purely chemical explanation of chromosome behavior and so 

 removes his interpretations from a direct comparison with the 

 work of others. Despite this extreme view he is constrained 

 to admit the presence of a chromosome series, constant in number 

 and in size relations, with an exact reduction of the euchromo- 

 somes- to the haploid number of maturation. No other investi- 

 gator has made an appeal from morphological conceptions and 

 since Granata' s interpretation is purely theoretical it need not be 

 discussed further, while so much remains to be done by observa- 

 tion. 



For the second possibility there are more advocates, although 

 it is often rather by inference than by exact statement that this 

 appears in the accounts. For while some profess a belief in the 

 genetic continuity of the chromosomes they yet describe a double 

 longitudinal division or a double cross division. Persistent 

 chromosome individuality is, however, possible only in the pres- 

 ence of a segregation, or reduction division during maturation. 

 With this understanding of the case Wilcox and Otte, conceiv- 



2 The word 'euchromosome' I shall employ to distinguish those \Yithout any 

 marked peculiarities of form or behavior. Montgomery's term 'heterochromo- 

 some' might advantageously be used as an antonym, signifying any general varia- 

 tion of structure or behavior. Subclasses within the general term heterochromo- 

 somes could be constituted under the headings 'idiochromosomes' (Wilson) to 

 include paired sex chromosomes; 'accessory chromosome' (McClung) to distin- 

 guish the unpaired sex element; 'microchromosomes' (Wilson) to designate small 

 compact chromosomes not connected with the sex chromosomes. I believe it 

 much preferable to use the genetic word 'chromosomes' in all terms denoting such 

 cell elements and to mark their specific differences by qualifying terms, rather 

 than to cojn entirely new names for them in which no intimation of their relations 

 is included. 



