1 86 ROBERT H. BO WEN. 



ing. Ordinarily they conjugate very briefly on the spindle ( \Yil- 

 son, 'O5&), and then separate precociously; but in this case they 

 seem to have gone on the spindle entirely separate from each 

 other (even their customary semblance of synapsis has failed). 

 One gets the impression that they receive spindle fiber attachments 

 at both ends, although a single one might be expected if such at- 

 tachments are invariably specific. 



The origin of the third centriole in a case of this kind is ob- 

 scure, but it is possible that a tripolar spindle might arise through 

 the precocious separation of one of the pairs into which the cen- 

 trioles of the hemiptera are characteristically divided at an early 

 stage in the growth period of the primary spermatocytes ; but the 

 staining of the centrioles in the case which I have described was 

 not sufficiently precise to permit analysis of this possibility. 



CASE 2. 



Cases in which normal, bipolar spindles are developed in con- 

 nection with an unusual number of chromosomes are of not infre- 

 quent occurrence. The best known examples are to be found in 

 triploid and tetraploid " mutants," in which the abnormal chromo- 

 some number exists in all the cells of the body. Similar multi- 

 plications of the normal chromosomal complex likewise occur in 

 the germ cells of normal individuals with some frequency, either 

 as isolated cases or in groups. Henking ('91), who first made 

 a critical examination of hemipteran chromosomes ( in Pyrrhoc- 

 oris), seems to have noted a case of the occurrence of the diploid 

 chromosome number in the first maturation division ( Henking 

 ('91), Fig. 300). though his explanation of the make-up of the 

 doubled chromosomes now seems doubtful. He noted also the 

 occurrence of a tetraploid connective tissue cell, an abnormal 

 condition commonly (if not constantly) present in the cells which 

 form the sheath of the hemipteran testis and its smaller subdivi- 

 sions. Hartman ('13) has more recently reported several cases 

 in the spermatogonia and primary spermatocytes of the grass- 

 hopper (Schistocerca and Alclanoplns] in which extraordinary 

 chromosome numbers were encountered. Morgan ('15) has re- 

 ported a case in Phyllaphis which differs from the above in that 

 a considerable number of cells are affected rather than a few 



