72 TJniversitij of California Publications in Zoology [Vol. 20 



Its significance is problematical. No evidences of sex or sexual 

 behavior have thus far been found in these flagellates. Hartmann 

 (1910), it is true, has described both male and female forms in his 

 Trichomjmpha hertwigi. His observations, however, do not bear out 

 this assumption. No critical evidences of conjugation were found 

 by him, neither in the behavior of conjugating gametes nor in the 

 nuclear changes which precede this process. Indeed, it is evident 

 to anyone familiar with taxonomic conditions in the Protozoa, that 

 his male and female forms belong to different genera, as has already 

 been pointed out by Grassi (1911). In his "junge, mannliche, and 

 weibliche" forms he has confused three distinct species and even 

 genera, with a fourth species added to this confusion in the "gametes" 

 which are minute oval flagellates such as are frequently abundant in 

 the intestinal contents of many termites. His elaborate life cycle of 

 this form is thus seen to be without adequate foundation, the product 

 of an overwrought creative imagination. 



This lack of evidence of sexual behavior in these organisms renders 

 doubly difficult any explanation of the significance of the function 

 of this peculiar structure. It remains distinct throughout both the 

 vegetative and division cycles, dividing in the metaphase, its position 

 that of a lagging chromosome in the anaphase, with one part going 

 to each daughter nucleus. At some stages it bears a strong resem- 

 blance to the chromatoid body described by Wilson (1913) in the 

 sperm cells of Pentatmna and some other insects. Its further behavior, 

 however, clearly distinguishes it from that body, which is cytoplasmic 

 in origin and does not divide. In Trichonympha this body has never 

 been found outside of the nucleus and behaves as do other chromo- 

 somes at the time of division. As a convenient designation for this 

 body and one which leaves its specific function still open to investi- 

 gation, we have used the term heterochromosome, since that word, 

 though originally used for the sex chromosome, has come to be 

 applied to other forms of chromosomes as well (Wilson, 1911). The 

 possibility is still open that further investigations may find undoubted 

 evidences of sexual behavior in these flagellates. 



Certain other aspects of mitosis in Trichonympha show striking 

 resemblances to the mode of procedure found in the division of 

 metazoan germ cells. The most remarkable of these is found in the 

 "pairing" of the chromosomes with a reduction of their number from 

 fifty-two to twenty-six (pi. 9, figs. 44-51a.). This pseudosynapsis, 

 however, may be explained on grounds other than that of sexual 

 behavior and our interpretation of it follows. 



