SYNGONISM 



(S. s.451) 149 



FIG. 16. Mononchus ma- 

 jor. I Side view of male. 

 II Side view of head of 

 same. Ill Front view of 

 head. IV Side view of tail 

 V. Details of male supple- 

 mentary organs. 



a, mouth 



b, lip-papilla 



c, lip 



f, pharyngeal tooth 



S, innervated papilla of skin 



h, oesophagus 



, base of pharynx 



flexure in testicle 

 blind end of testicle 

 vas deferens 

 lip 



*, accessory piece 

 u, post-anal i 



v, spicula 



papillae 



iv, ejaculatory duct 



x, ventral row male papillae 



y, an 



than is usually the case in the remainder of the series ; thence forward 

 the organs are about equidistant. Usually they are more or less con- 

 tiguous, though occasionally they are separated by short spaces, especially 

 anteriorly. When most highly de- 

 veloped, each is a convex-conoid, 

 innervated, very minutely papil- 

 lated or echinulate, more or less 

 protrudable organ, connected with 

 the interior by an oblique, indis- 

 tinct element along the axis of 

 which a nerve passes inward and 

 forward to join the ventral nerve 

 of the body (v, fig. 16). It would 

 appear that these organs are partly l ; n> 

 tactile and partly excitatory in *; 

 function, and act as the comple- J; ^jacSatM^duct 

 ments of the vulvar papillae of the r ; ^"fetory duct 

 female. There is no bursa. The 

 series of oblique copulatory mus- 

 cles is always coextensive with 

 the series of supplementary or- s - three anal R lands 

 gans. The rather short testes seem to be invariably two in number and 

 are outstretched in opposite directions. The spermatozoa of males are 

 minute and present a more or less vermiform nucleus. 



Self -Fertilizing Females; Syngonism 



Males Rare. Conjugation of Syngonic Gametes. No trait of mon- 

 onchs is more interesting than the capacity of the female to reproduce 

 without the intervention of a male by a peculiar sort of hermaproditism 

 called syngonism. Of most of the species no males are known; in the 

 remaining species, almost without exception the males are very scarce, 

 and only in exceedingly rare cases are they present in anything more 

 than small numbers. Usually hundreds, and even thousands, of speci- 

 mens may be examined without the discovery of a single male. How 

 then do the females reproduce? The answer is singularly interesting, 

 for, as already explained, the females fertilize their own eggs by means 

 of spermatozoa which they themselves produce in the same gonad. In 

 the mononchs these spermatozoa produced by females are so exceedingly 

 minute that they have hitherto escaped notice (fig. 2). Notwithstanding 

 its small size, the syngonic sperm cell appears to be functional. It enters 

 the egg, expands, and approaches the nucleus of the egg, which mean- 

 while throws off polar bodies and later proceeds with segmentation. 

 Observations have not yet extended beyond this point, but it saems alto- 



