ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 535 



spermatogenetic, activity were insufficient to provide spermatozoa for 

 all the eggs. 



(5) Among the hermaphrodites a few males may occur — 0*13 per 

 1000 for Diphgaster robustus, 1-5 per 1000 for Bhabditis elegans, 7 per 

 1000 for B. perrieri, 20 per 1000 for B. duthiersi, 45 per 1000 for 

 B. viguieri. There is nothing abnormal in the structure of these 

 occasional males. (6) They seem, however, to have almost quite lost 

 their sexual instinct and appetite ; they have the inertia of females ; 272 

 were placed with 313 females, and 20 fertilisations occurred — 13 in one 

 species (B. marionis) whose hermaphroditism is incomplete. (7) They 

 may be called atavistic males, reminiscent of the primitive dioecism. 



(8) The progressive elimination of the male type is forcibly sug- 

 gested by the partial hermaphroditism of some forms in which the gonad 

 of one side occasionally produces eggs only (B. duthiersi), or in which 

 this may be true even of both gonads (B. marionis and B. viguieri). 

 In these species the occurrence of occasional males is most frequent, 

 viz. in the order mentioned, 20, 7-6, 45 per 1000 females. (9) This 

 implies a substitution of the hermaphrodite for the dioecious state, and 

 Maupas argues that this and not the opposite process has been tbe 

 general mode of origin of hermaphroditism. (10) It also seems clear 

 that the hermaphroditism has been evolved only in the feminine type, 

 which conserves the more primitive characters. (11) Everything points 

 to the general conclusion that the male and female germ-nuclei are 

 absolutely equivalent, both morphologically and physiologically. 



(12) In B. elegans, B. marionis, and B. duthiersi, the occasional 

 males were got to impregnate hermaphrodites which had exhausted 

 their own sperm. In the two last-named species the issue of this 

 heterogamic fertilisation resulted in quite normal individuals ; in B. 

 elegans there was a marked " arrenotokous " influence, the proportion of 

 males (usually 1-2 per 1000) rose to 463 per 1000, re-establishing an 

 approximate equilibrium of the sexes, or, more strictly, resulting in an 

 approximate equilibrium between hermaphrodites of feminine build and 

 quasi males ; for these males were as usual practically non-sexual — 

 they did not copulate. 



(13) Experiments on B. elegans and B. canssaneli as to the possible 

 influence of age and nutrition on the numerical proportions of the sexes 

 gave no result, except that the total number of eggs was greater when 

 the food was abundant. The sexuality of the individuals and of their 

 reproductive cells is irrevocably determined from the time of the 

 maturity of the original germ-cells, i.e. from the beginning of the life of 

 the parent. 



(14) The continuance of autogamic reproduction was observed in 

 three cases for 40-50 generations, and the result was always degeneracy 

 — abortion, weakness of larvae, sterility. But the degeneracy always 

 appeared suddenly, when the surrounding temperature rose to 23°-24° C., 

 and Maupas thinks that the rise of temperature was really the cause. 



(15) Seven parthenogenetic species (in six genera) were observed — 

 Rhabditis schneideri, Cephalobus dubius, C. lentus, Plectus cirratus, Aphe- 

 lenchus agricola, Alaimus thaumugadi, Macrolaimus cruris. Of the first- 

 named, 4039 adults were observed, without hint of a male ; but the 

 author admits that males may occur as rarities. (16) In conclusion. 

 Maupas refers to the extraordinary reproductive diversity which his 



2 O 2 



