436 F. A. POTTS. 



Ill 1900 Maupas,^ in a l^rilliunt paper, drew attention to many 

 striking" features in the reproductive phenomena of such 

 npecies. A full description of uW prior work rehiting to 

 liermaphroditisrn in the Nematoda is given by Maupas, and I 

 shall lieie content myself with a short resume of liis own 

 results, which later will be quoted more in extenso in 

 connection with my own observations. 



The species of the free-living nematodes Rhabditis and 

 Diplogaster fall into one or other of three categories : 



(1) Bisexual species, in which male and female individuals 

 are produced in equal numbers. 



(2) Hermaphrodite species, in which, besides the self- 

 fertilising protandrous hermaphrodites Avhicli form the great 

 mass of the species, there are occasional male individuals, 

 perfectly developed apparently, but taking no part in repro- 

 duction. 



(3) Parthenogenetic species, in which males have not been 

 found. 



It is reasonably supposed that each hermaphrodite species 

 is derived from a bisexual form by the development of 

 spermatozoa in the ovary of the female individuals, which 

 thus become self-fertilising. 'J'he males are now useless, and 

 have even to a large extent lost their sexual instinct. Their 

 number dwindles in most cases to an almost imperceptible 

 figure, but final disappearance does not appear to be reached 

 in any species, and this persistence of apparently useless forms 

 is one of the most curious facts recorded in biology. 



The hermaphrodite species appear even more numerous than 

 the bisexual. There is, indeed, some evidence that the con- 

 version of females to hermaphrodites in the bisexual species is 

 a present-day process, furnished by the examples of partial 

 hermaphroditism described by Maupas. An intermediate 

 condition is shown iu some hermaphrodite species by the 

 occasional occurrence of pure females, or in the production of 



' E. Maupas, "Modes et Formes de Reproduction des Nematodes/' 

 *Arch. de Zool. Exp. et Gen./ Ser. 3, X. 8, 1900, pp. 463-624, Pis. 

 xvi-xxA'i. 



