58 WALTER K. FISHER, 



The left osphradiuni is somewhat larger than the right, and both 

 appear as mere yellowish, elongate lumps on the "neck". In cross 

 section these are seen to be produced forward, and the substance of 

 the organ is made up of a curious spongy connective tissue sharply 

 defined from the muscle layer of the body wall, beneath. In this 

 meshy tissue are seen blood cells, ganglion cells and nerves. The 

 epithelium is low, almost cubical and seems to differ little from that 

 covering the surrounding head wall, except in the clearer more brightly 

 staining nuclei. 



The eye is a pear - shaped pit near the base of the tentacle 

 (Fig. 29) and opens to the exterior by a very narrow pore. Un- 

 differentiated epithelium lines the portion nearest the opening, and 

 extends farther down on one side of the cavity than on the other. 

 The "retinal" epithelium is high and very heavily pigmented. The 

 lumen of the eye-pit is filled with congealed humor, which tends to 

 form a definite columnar layer next to the pigmented epithelium. 



I have not followed out the finer structure of the otocysts. In 

 sections one can readily see the minute granules which are found in- 

 side. As shown by Fig. 28 each is shaped like a little apple seed, 

 and is imbedded in connective tissue, beneath the pleural ganglion. 

 Three connective tissue stays or ligaments hold the structure firmly in 

 place. One (Lig. Fig. 28) connects the two otocysts, while two others 

 bind each to the pleural and to the pedal ganglion of that side. 



Summary. 



A summary of the more important points in the anatomy of 

 Lottia are here given, following the order of the preceding text. 



1) The Acmaeidœ possess a larval nautiloid shell. 



2) The lips are armed with tiny teeth. 



3) Within the oral cavity there are two well-developed palps, 

 which receive an abundant supply of nerves from the labial ganglia, 

 and function probably as taste organs. 



4) A sublingual or subradular organ innervated from the sub- 

 radular ganglia is present, situated under the tip of radula. 



5) There are two pairs of buccal glands, the anterior opening by 

 long glandular ducts into the oral cavity, the posterior by the separate 

 acini into the swollen pharyngeal sac. 



6) The pharynx is thin-walled and dilated, and divided into lateral 

 pockets by frequent constrictions. Into these the posterior salivary 

 glands empty. 



