180 IOWA ACADEMY OF SCIENCES. 



each organ opens into the pericardial cavity, and at the other 

 end into the cloacal chamber. Pig. 1, o B, shows the right 

 organ as seen from the left or inner side, and Fig. 7 is a dia- 

 gram of the left organ as seen from the left or outer side. By 

 comparing the two figures the relations of the loops will be seen. 

 The cells lining the organ are apparently not glandular in the 

 immediate vicinity of the pericardial opening, and are rather 

 small near the cloacal opening, but throughout the rest of the 

 tube the cells are large and vacuolated, as shown by Fig. 11, 

 which represents specially large cells from the dorsal part of 

 the organ. I have been unable to find cilia on any of the cells. 



REPRODUCTIVE ORGANS. 



The animal is hermaphroditic. The reproductive organs, 

 which are paired, each consist of a racemose gland. Pig. 1, r o, 

 situated beneath the pericardium and behind the stomach, 

 varying in extent according to the age of the individual, and 

 opening into the cloacal chamber close to the cloacal opening 

 of the organ of Bojanus. Part of the follicles bear ova, oth- 

 ers sperm. The ova-bearing follicles are generally among those 

 most posterior. They are fewer in number than the sperm 

 follicles, and, in this species, bear comparatively few ova. 

 Fig. 8 represents a section of an ova-bearing follicle, in which 

 are a number of nearly or quite mature and several very young 

 ova. The sperm-bearing follicles are generally full of sperm, 

 which lie free in their cavities. Reproduction, apparently, 

 goes on during the greater part of the year. 



LITERATURE. 



1. Brooks, W. K. Sensory Clubs or Cordyi of Leodice. Jour, of Morph. 



Vol. X, No. 1. 



2. Kellogg, James L. Contributions to our Knowledge of Lamelli- 



brancliiate Mollusks. Bui. U. S. Fish. Commission, 1890. 



3. Lang, Axmold. Lehrbuch der Vergleichenden Anatomic. 



4. Lankester, E. Ray. Mollusca. Enc. Britt. 



5. Leydig, Franz. Ueber Cyclas Cornea. Miiller's Archiv., 1855. 



6. Mitsukuri, K. On the Structure and Significance of some Aberrant 



Forms of Lamellibranchiate gills. Quart. Jour. Mic. Sci., Vol. 

 XXI, 1881. 



7. Peck, R. H. Gills of Lamellibranchiate Mollusca. Quart. Jour. Mic. 



Sci., Vol. XVII, 1877. 



8. Pelsener, Paul. Contribution a I'etude des Lamellibranches. Arch. 



de Biol., Tome XI, Part 2, 1891. 



9. Rankin, AValter M., tjher das Bojanus' sche Organ des Teichmuschel. 



Jena, Zeit. Bd. XXIV, 1890. 

 10. Zeigler, E. Die Entwickelung von Cyclas cornea Zeit. f. Wiss. Zool. , 

 Bd. XLI. 



