JOURNAL OF ENTOMOLOGY AND ZOOLOGY 145 



large gang-lia, similar to the braueliial and genital, were visible, 

 such ganglia as appeared being very minute. The genital 

 plexus is greatly fused, forming a single ganglion as large as 

 one of the buccal ganglia, which gives off several nerves to 

 the reproductive organs, as well as one nerve (12) to the body 

 wall, which is apparently homologous with (13). The branchial 

 plexus consists of several fairly large ganglia, which give off 

 larger nerves than are found in other portions of the accessory 

 system. The central ganglion receives a nerve from the vis- 

 ceral ganglion and branches from the posterior mantle nerve, 

 these latter having passed through ganglia which give off 

 branches to the heart and brancliial region. The central 

 ganglion gives oft' branches to the nephridia and the region 

 around the intestine, and is joined to a small ganglion just 

 above it, which gives nerves to the three branchias. 



The Sense Organs. The otocysts are buried between the 

 cerebro-pleural and pedal gangiiaT just inside the eerebro- 

 pleural and pleuro-pedal connectives. They are oval mem- 

 branous capsules about 50 microns long, lined with a few much 

 elongated cells. The otoconia appeared to be very small par- 

 ticles, but they may have been partly eroded by the acid used 

 in the iixing solution. 



The eye is nearly globular and slightly elongated from front 

 backwards, where it measures about 75 microns. It lies in a 

 mass of connective tissue somewhat in front of the optic 

 ganglion, to which it is attached by a very small nerve. The 

 coat of the eye itself is a thin, compact, connective tissue layer, 

 much thinner in front than in liack. The lens is nearly oval 

 and in section appears to be formed of a thick capsule, contain- 

 ing an alveolar substance, or at least, a substance that con- 

 denses into globules after fixation. Back of this is a thick 

 cap-shaped layer of pigment granules, and back of these and 

 closely connected with them are a few cells of rather indefin- 

 ate outline, containing large granular nuclei, very similar to 

 the nuclei of some of the nerve cells. The whole appearance 

 and location of the eye would indicate that it does not fulfill 

 any very important function. It is not only situated below the 



