34 OPISTHOBRANCHIATA OF BRAZIL 



of the pleuro-parietal connective, simply receiving a small anasto- 

 mosing branch of the first parietal nerve. 



The second (r. p. 2}, is a very large nerve originating from 

 the dorsal side of the posterior end of the parietal ganglion. It 

 passes backward for a short distance, and terminates in a good 

 sized ganglion, lying below the integument in front of the 

 branchia. From this ganglion a nerve is sent to the ctenidium 

 and the wall of the branchial chamber, another penetrates deeply 

 among the muscles of the body wall, in front of the kidney and 

 is probably distributed to the mantle, though its course could not 

 be made out with certainty. The main portion of the ganglion 

 supplies the osphradium, or organ of Spengel, a conspicuous oval 

 elevation with a depressed center, situated just in front of and 

 slightly above the base of the ctenidium. 



THE REPRODUCTIVE SYSTEM. 



The excellent work of Mazzarelli ('91) upon the reproductive 

 apparatus of the Aplysiidae has cleared up many doubtful points 

 in the structure and functions of this complicated system, though 

 much remains still to be done. In the following discussion of 

 this system in Tethys dactylomela I use the nomenclature adopted 

 by him. 



The reproductive system of the Aplysiidae is made up of the 

 following structures, given in their order of occurrence from 

 behind forward. 



1. The ovotestis, or hermaphroditic gland. 



2. The small hermaphroditic duct. 



3. The adnexed genital mass, consisting of the nidamental 

 and albumen glands, the fertilization chamber, and the con- 

 voluted and spiral portions of the genital duct. 



4- The spermatocyst and duct of Cuvier. 



5- The large hermaphroditic duct. 



6. The spermatotheca, or vesicle of Swammerdamm. 



7- The external spermatic groove. 



8. The penis and its sheath. 



The ovotestis forms the posterior end of the visceral mass, 

 being more or less extensive depending upon the degree of sexual 

 maturity of the individual. In the largest specimen at hand 

 (140.0 mm. in total length) the ovotestis is large, flattened 



