A CONTRIBUTION TO OUR KNOWLEDGE OF THE 



REPRODUCTIVE ORGANS OF THE NUDI- 



BRANCHIATA. 



By Thomas Frederick Dreyeu, li.A., Ph.D. 



This ipaper is the result of work done preparatory to my 

 former thesis (1) on the Nudibratichs ; it has l:)een written up 

 in South Africa, and it is therefore impossible to give a good 

 resume of the recent literature. Its incompleteness is due to a 

 lack of opportunity to work owing to my constant movnig about in 

 pursuance of my official duties. Only one species, Dofo fragilis. 

 have I been able to work up in detail ; the others 1 shall describe 

 briefly, diagrammatically. 



DoTO Fragilis. 



Named specimens were obtained from the Board of Fisheries. 

 Plymouth. 



The relative sizes and positions of the various organs can, 

 of course, be much better demonstrated by means of dissections, 

 and for such information I can refer to Alder and Hancock (2), 

 Fig. 15, Fam. 3, PI. 4. These authors do not, however, label the 

 viarious parts either fully or correctly; e.g., wliat is really the 

 hermaphrodite gland they take to be the same structure as that 

 which they call " ovarium " in the genus Eolis. Pelseneer (3) 

 ocrrected this error, but incorrectly generalises, for his group of 

 " Elysiens "' — to which both Doto and Eolis belong — that every 

 acinus contains ova in one half and spermatozoa in the other. 

 Trinchese (4) (for .Janu.<i cri.<;tat\ts) . and Bergh (5) for Ri.z,zolia, 

 PI. I, Fig. 9, Treveiyana, PI. 4, Fig. 10, etc.), have described the 

 structure of hermaphrodite glands as I find it in Doto fragilis. 

 Bruel (6) has shown in the case of CaliphyUa lueditcrranea 

 (also an Elysicn) thdt each acinus is, in its young stage, lined 

 by intermixed egg-mothercells and sperm-mothercells ; that the 

 spermatozoa begin to ripen first, and that the ova, as they in- 

 crease in size, are forced in between the epithelium of the acinus 

 and the basal-cells of the spermatids ; that each old acinus has 

 thus a peripheral layer of ova and a central mass of spermatids 

 and spermatozoa. 



In Doto fragilis the hermaphrodite gland is divided into a 

 large number of units, each composed of a central chamber 

 for the production of spermatozoa and a number of much smaller 



