goediidjE. 57 



alimentary canal terminates by a coecum near the middle of the body, 

 and not, as Eobin and myself had supposed, by an anal outlet. In 

 other anatomical arrangements the various species of Gordiidge vary 

 still more strikingly, especially as regards the disposition of the 

 reproductive organs. In all, however, the sexes are distinct, and 

 they are parasitic during a portion of their life-time, the greater 

 number taking up their temporary residence within insects, whose 

 bodies they penetrate from without. In the same manner the 

 female of the Guinea-worm, or Dracunculus medinensis, gains 

 access to the sub-integumentary tissues of the human body ; but 

 it does not apparently seek to imitate the Gordii proper by volun- 

 tarily quitting the host at a comparatively early stage of its life- 

 period. The Gordii, after their escape, deposit multitudes of ova 

 in long agglutinated chains either in water or moist situations ; 

 the Dracunculi, on the other hand, reproduce viviparously, the 

 young being discharged whilst the parent is still lodged within its 

 host. All the Gordiidse, like their anguilluline congeners, are 

 remarkably tenacious of life, and both in the young and adult con- 

 ditions, will endure complete desiccation for a lengthened period 

 without injury to their vital powers. 



Reserving my account of the general anatomy and development 

 of Dracunculus for the second part of this work, I purposely select 

 the genus Mermis as a type of the family under consideration. In 

 Gordius the integument is smooth externally, presenting, when 

 highly magnified, a beautifully reticulate arrangement of the 

 epithelium, but in Mermis the skin near the head is furnished 

 with a variable number of papillary eminences which are probably 

 homologous with the more numerous wart-like eminences so charac- 

 teristic of the singular genus Sphserularia. In the year 1842, 

 Dujardin ably investigated the anatomy of Mermis nigrescens.* 

 He describes the integument as being composed of three distinct 

 layers ; first, an external homogeneous epidermis, which is readily 



* Annales des Sciences Naturelles ; 2e serie, tome xviii., p. 129. 



I 



