428 Sidney I. Kernhäuser 



we niust lay less importance on the material composition of the chromosonie 

 and say that the size of a chromosonie is no indication as to the number 

 of determiners it bears, viz. that in one species (as C. viridis var. hrevispi- 

 nosus) a given chromosome can bear as many determining substances 

 as two or three chromosomes eqiially as large in another species (as C. 

 strenuus); or, (2)weniustconsiderthatthe chromosomes in phylogenetically 

 recent forms carry merely the specific or varietal determiners and per- 

 haps the sex determiners. The latter proposition demands that, outside 

 the chromosomes (in the cytoplasm or other constituents of the cell), lay 

 the determiners w"hich roughly guide and shape the development of the 

 organism so that, let us say, a Copepod must result with the characters 

 of a member of the genus Cyclofs, bnt along with this development come 

 the effect of the chromosomes which tend to the finer details and settle 

 to which species this Cyclops shall belong. If this be true, then there 

 would be little chance of finding many homologons chromosomes even 

 between species of one genus or the species of nearly related genera of 

 highly specialized organisms. Theeliminationof themajorityofthepata'nal 

 chromosomes in sea-urchin crosses (Baltzek '10), and the failure of the 

 majority of chromosomes to conjngate in the germ cells of Lepidoeteran 

 hybrids (Federley '13, '14) would stand in favor of such a view. 



As to when or how the generic determiners become located outside 

 the chromosomes, little can be said. Braun ('06) and Matscheck ('Ol) 

 described micro- and hetero-chromosomes (loc.-cit. p. 432) for various 

 species in the genus Cyclops. These are usually much smaller than the 

 tetrads, are sometimes paired, sometimes unpaired, and seldom show a 

 "Querkerbe". Matscheck describes the hetero-chromosome in Cyclops 

 vernaUs as sometimes being present and sometimes absent. Both of these 

 authors consider the hetero-chromosomes oiCyclops, not as sex-determiners, 

 but as stages in the disappearance of chromosomes. Whether this gradual 

 diappearance (?) of a chromosome is connected with the transfer of deter- 

 miners to other constituents of the cell must remain an open question. 



If thcn we find it impossible to homologize the chromosomes of 

 closely related species and genera, is there still something distinctive in 

 their form or size which may be of use from a systematic standpoint as, 

 for example, the complex hexad or octad occurring throughout the various 

 species of certain Orthopteran genera (McCluxg '08), or the large curved 

 pair of chromosomes met wdth in so many Homopterans (Stevens '06; 

 BoRiNG '07, '13; KoRNHAUSER '14)? In a comparison of the spermato- 

 cytes of insects, a certain character in the form of the chromosomes and 

 spindle is distinctive of each of the larger sub-divisions, under which 



