Introduction to Animal Morphology. 1 79 



encysted therein ; its perfect forms are found in Orthopterous 

 or Neuropterous insects, which it again leaves for repro- 

 duction, and becomes free, losing its mouth and intestine. 

 2. IMermidas — thread-like ; oesophagus short; head papillary; 

 tail undivided papillary in the male, with a double penis 

 (spiculum, spermategae of Dicsiiig) ; egg-shells often with 

 brush-like tassels ; eggs not in chains as in Gordius ; uterus 

 two-horned ; larvae with single cephalic spines, found in 

 Lepidoptera, &c. 3. Sphserularidse — in the body cavity of 

 Bombus ; with no mouth nor oesophagus (or a mouth opening 

 into the body cavity ?) ; skin with vesicles ; male small, 

 vrroou of the size of the female, to which it is organically 

 fastened ; female with a simply tubular ovary, a terminal 

 genital opening, and two rows of large cells in the body 

 cavity. 



Order 2. Nematoda [Rudolphi) — free or parasitic 

 round worms, with a smooth, never ciliated, some- 

 times double refracting cuticle ; rarely with bristles 

 or lateral wing-like expansions beside the head (these 

 are sometimes inconstant, as in Ascaris dactyluris). 

 This layer is chitinoid, and sometimes makes the body 

 stiff, but is less resisting to re-agents than the chitin of 

 Arthropods ; it is traversed by fine pores, often annu- 

 lated, transversely striped, or laminated, the superficial 

 layers being the most chitinous. The dermis is 

 thinner, obliquely striated, made of granular proto- 

 plasm, and longitudinal and vertical connective fibres ; 

 it is often traversed by laminae, and sometimes con- 

 tains unicellular glands. In Trichocephalus, there is 

 a ventral row of rod-like bodies in the dermis. In 

 Trichosoma, a ventral and dorsal row ; in others, 

 nail-like rods. Young nematodes usually moult several 

 times. The muscular lamina, thicker than the inte- 

 gument, as it is in most Vermes, consists of two sets 



N 2 



