VI TRACTICAL DIRECTIONS 375 



posterior end of the heart, and running along the dorsal side of the 

 intestine, giving off branches in each raetamere ; c, the sternal artery, 

 arising jiist beneath d, and passing directly ventralwards to one side of 

 the intestine (this will be seen better later on : compare Figs. 86 and 

 87} : it perforates the ventral nerve-chain, supplies the segments and 

 appendages of the thorax, and gives off a z'eufral atidominal artery, 

 supplying the segments and appendages Oi the abdomen (this artery can 

 be seen in injected specimens through the transparent cuticle). 



5. Note the position of the following parts before dissecting further : — • 

 a, the f'/:;rt;r/, a large sac in the head, with two pairs of muscles passing 

 to the integument (now^ cut through) ; b, the additetor iintsi/es of the 

 mandible, just external to a ; (■, the paired, brownish or greenish diges- 

 tive gland on either side of, and extending further Ijack than the 

 gizzard ; aljove il are d, the gonads, on either side of and behind the 

 pericardial sinus. In the male, the sperniary is small and whitish, and 

 each spermidnct is a coiled, densely white tube ; in the female, the ovary 

 Is a larger, brownish organ, containing prominent oi'a. (In both sexes, 

 the paired character of the gonads is partly lost by fusion : a pair of 

 anterior lobes and a single posterior lobe can be seen in each. ) Sketch. 



By slightly raising the surrounding parts the gonaducts can be seen to 

 pass ventralwards to their external apertures (p. 373), the oviducts 

 being thin-walled and straight. White masses, the spermatopliores 

 (p. 368), will very likely be found stuck on to the sternal region of the 

 body. 



6. Tease up a small portion of the spermary or of a spermatophore ; 

 stain, and mount in glycerine. Examine under the microscope and note 

 the rounded and flattened sperms each with a number of stiff, curved 

 processes coming off from the periphery. The sperms are non-motile. 

 Sketch. 



Remove the heart and reproductive organs carefully, noting the 

 sternal artery (see above) as you do so, and taking especial care not to 

 injure the surrounding parts. Examine the heart under water, and 

 note the six ostia. 



II. The enterii canal. Note — I. The oval ?;w«M, bounded by the 

 labritm in front, leading into a short and wide gullet (this will be seen 

 later on), which dilates to form the large gizzard (Fig. 86), filling up 

 a considerable portion of the head and extending into the thorax : a 

 transverse constriction divides it into an anterior and a posterior 

 portion ; both gullet and gizzard are lined by chitin. The chitinous 



