made at Naples in the winter o/* 1871-72. 91 



I should mention that one fact in favour of regarding the 

 mulberry spheres as testicular is that when thej abound the 

 ova appear to be absent, and vice versa. This is only apparently 

 the case ; for I have found numerous ova (though far less numer- 

 ous in proportion than elsewhere) in Sipiinculi in which the 

 mulberry spheres were predominant, and I have noticed young 

 stages of the mulberry spheres present when ova abounded. 

 It should, however, be noticed that all the full-grown Sipun- 

 culi (some eighty-five in number) which I opened were di- 

 stinguishable as either " ova-bearing " or " mulberry-sphere- 

 bearing." 



Brandt and, in earlier years, Krohn have been the supporters 

 of the view that the mulberry spheres are testicular ; but 

 neither of them has seen the development of the component 

 spherales of the spheres into tailed spermatozoa. Brandt states 

 that he found in May, in a Sipunculus of the mulberry-sphere 

 kind, tailed spermatozoa floating in the perivisceral fluid. But 

 he admits that such spemiatozoon-like bodies are developed in 

 the brown tubes ; and he has no evidence whatever to prove 

 that those he found in the perivisceral fluid had not come thence, 

 especially since he obtained the fluid by puncture and might 

 thus have wounded the brown tubes. 



I must yet further mention with regard to the pink corpuscles, 

 that I sometimes found them of large size and containing crystals 

 — a fact not noticed by Brandt ; also in May I noticed cases in 

 which they were all very small, and in which only a few loosely 

 aggregated mulberry spheres and no ova were present. I believe 

 that the reason why mulberry spheres and ova are reciprocally 

 exclusive in the perivisceral fluid is this, that after tlic ex- 

 pulsion of the ova a renewal of the pink corpuscles is necessary, 

 and accordingly we get this development of mulbeny spheres, 

 destined to break up into young pink corpuscles. It is not until 

 the spheres have fully developed and broken up into young- 

 pink corpuscles that a new development of ova takes place, by 

 detachment from the rectal arborescent villi. The testis is either 

 the tissue on the intestinal diverticulum or the brown tubes ; 

 which of the two, my notes and drawings do not decide. 



The termination of nerves in the skin, the cutaneous glands, 

 the minute structure of the nerve-chord, the structure and 

 varieties of connective tissue in various pai'ts of the worm, and 

 the curious pink or red line on the intestinal wall, which is not 

 a vessel, were examined, and Avill be described and figured on 

 a future occasion. 



Brandt's description of the perforate structure of the egg- 

 envelope is perfectly correct. 



