308 



ZOOLOGY 



prevented as if the organs of the two sexes were distinct. A 

 totally different arrangement is met with in the Nematomorpha, 

 the female having numerous pairs of ovaries (Fig 247, A, ovy.) 

 arranged segmentally and attached to one of the partitions (mes.) 

 of the body-cavity. The ripe eggs are discharged into large 

 egg-sacs, formed by the lateral compartments of the body-cavity, 

 and finally make their way into the medio-dorsal compartments 

 which act as uteri (C, itt.) and are continued posteriorly by short 

 vaginae (vag.) into a median chamber. The latter opens externally, 

 and also receives the duct of a large spermotheca (spth.) or chamber 

 for storing the sperms received in copulation. In the male 

 Gordius the testes are not known : they seem to disappear very 



s P tfl v.nv.cd v<*g 



Pio. 247.— Gordius. A, horizontal section of female, showing ovaries (nvy) attached to mesen- 

 tery (me*.) ; 6. w. body-wall. B, posterior extremity of male, sagittal section, b. c. bursa 

 copulatrix ; cl. cloaca ; int. intestine ; t, tail ; v. nv.cd. ventral nerve-cord ; vs. sent, vesicula 

 seminalis. C, posterior extremity of female, sagittal section, gnp. gonopore ; spth. sperma- 

 theca ; ut. uterus ; vag. vagina ; v. nv. cd. ventral nerve-cord. (After Vejdowsky.) 



early, after discharging their contents into large reservoirs or 

 vesicidce seminales (B, vs. sem.) : from these, vasa deferentia are 

 continued into the cloaca (cl.) or dilated extremity of the intestine, 

 part of which can be everted as a bursa copulatrix (b.c). 



In the development of Nematodes segmentation may be un- 

 equal from the outset, or equal at first, becoming unequal after the 

 first two or three divisions. There may be an invagination (embolic 

 gastrulation), or, as in Rhabdoncma nigrovcnosum (Fig. 248) a kind 

 of epiboly , or a process of an intermediate character. The blastopore 

 always disappears, taking no part in the formation of the apertures 

 of the adult. The archenteron also becomes obliterated, and the 

 lumen of the intestine has no connection with it, but is formed 

 anew by the development of a fissure between the endoderm cells 



