II.] THE CRAYFISH AND LOBSTER. 21 5 



a. Two tracts of fibres, arising from the head of the 

 postero-ventral ossicle and attached — the slender 

 ventral one to the base of the antero-lateral 

 ossicle ; the fan-shaped dorsal one to the postero- 

 lateral bar. 



/?. A sheet of fibres, investing the side wall of the 

 pyloric chamber and usually broken up into three 

 fasciculi. 



The above-named constrictor muscles exercise 

 a direct control over the cardio-pyloric and other 

 '* valves " of the straining apparatus. 



y. The cardio-pyloric muscles; two delicate sheets, 

 seen, on carefully removing the cellular roof of the 

 stomach, to pass obliquely forwards and inwards 

 from the lateral-pyloric to the cardiac ossicles. 



g. The anal muscles ; extremely delicate tracts, passing 

 between the anal valves and the immediately ad- 

 jacent wall of the intestine. 



8. The digestive gland. Its general characters have 

 been previously described. 



a. Tease out a bit in water; it is made up of ccecal 

 tubes, which are seen to be lined by a large celled 



epithelium. 



« 



b. Submit a small piece to the action of i Vq solution 

 of Osmic Acid until well blackened. Examine in 

 water under a high power ; many of the cells will 

 be found to contain a fatty product, deposited in 

 globules, blackened under the action of the reagent. 



c. Prepare (as directed in the Appendix) transverse 

 sections of the frozen gland ; transfer them, as cut. 



