256 



Appendices to Fifth Annual Report. 



Fig. 32. Embryo '28 mm. in length. Foot well marked, gill-pa pillae appearing, 

 eye-spot, auditory capsule, anterior and posterior adductor muscles ; velum still 

 present. /, foot ; gp, gill-papilla? ; e, eye-spot ; ot, auditory capsule ; pa, posterior 

 adductor. 



Fig. 33. Spermatozoa, greatly magnified. 



Plate XIII. 



Fig. 1. Section* of young mussel (1*5 mm. in length) along the line of, and close 

 to, the foot-protractor. Is, larval shell ; prs, prismatic shell ; by, byssus-gland. 



Fig. 2. Transverse section of the mantle of a young female mussel, to show the 

 egg-folicles and their canals, gc, genital canal. 



Fig. 3. Longitudinal vertical section of the termination of the genital and excretory 

 canals, kt, excretory canal. 



Fig. 4. Transverse section of the genital tube of a male mussel, to show the ciliated 

 ridges and the free spermatozoa, s, spermatozoa. 



Plate XIV. 



Fig. 1. Transverse section of the mantle of an adult male mussel, to show the 

 sperm-follicles, sf, sperm-follicle ; ce, columnar, ciliated epithelium ; gc, germinal 

 epithelium. 



Fig. 2. A corresponding section of the mantle of a male mussel, half an inch long, 

 the single series of follicles occupying the whole breadth of the mantle. 

 Fig. 3. Embryo '188 mm. in length. 

 Fig. 4. Its expanded velum, from below. 

 Fig. 5. Portion of zoophyte clad with young mussels. 



Fig. 6. Ramifications of the generative follicles shortly after the reproductive 

 elements are shed. 



Fig. 7. Longitudinal section of a mussel 1*5 mm. in length, showing foot, 

 foot-retractor, foot-protractor, adductors of the valves, oesophagus, liver, gills, 

 parieto-splanchnic, pedal and cerebral ganglia. pr, foot-retractor ; pp, foot- 

 protractor ; psg, parieto-splanchnic ganglion ; pg, pedal ganglion ; eg, cerebral 

 ganglion ; pi, pallial-muscle. 



* The sections were stained with borax carmine. 



