TRANSACTIONS OB' SKCXION D. DKPT. ZOOLOGY AND BOTANY. 675 



nervous tissue pervades tlirougliout the body, as some time ago it was found to 

 exist in Actinirc and in certain Nemerteans. 



Lastly, another not uuimportant fact may be noticed : viz. that here the three 

 principal paii-s of nerves separately originate from the brain, which is not the case 

 in the other Amphineiira. 



The organs of reproduction and of excretion of Proneomenia are in many respects 

 highly suggestive. 



The hermaphrodite gland is situated all dlong the back of the animal ; it is very 

 symmetrical and intrinsically double. The generative products are carried by two 

 ciliated canals, which are tlie direct continuation of the double gland, into a cavity, 

 the pericardium. This pericardium in Mollusks is the representative of the body- 

 cavity : in Ch^toderma and Neomenia it equally serves as a receptacle for the eggs. 

 Inside this cavity in all the three genera the heart is situated, and caused the "ill- 

 chosen name of pericardium to be given to this reduced portion of the body-cavity. 



Another set of ciliated ducts leads the genital products out of the pericardium 

 towards the exterior. They are of different diameter and make a double bend. 

 A paired additional gland which is ramified opens out into them. The terminal 

 thicker portion of the ducts leading outwards has a high epithelium in which 

 spherical secretions take their origin. It is marked off by a muscular constriction 

 from the parts preceding it, and must, as it appears to me, be looked upon as the 

 renal organ, the kidney, of the animal. Both halves of it coalesce and then open to 

 the exterior. 



In this direct and serial continuity between the three cavities (a) of the genital 

 gland, (6) of the pericardium, and (e) of the kidney or nephridium, I believe we have 

 an important fact before us for the comparative morphology of the Mollusks. Now 

 we must bear in mind (1) that in the greater number of Mollusks a communication 

 between the renal organ and the pericardium {i.e. between the nephridium and the 

 body-cavity) persists. Secondly, that the genital products, which are generally 

 carried outwards independently, are, on the contrary, evacuated into the cavity of 

 the kidney in such more primitive Mollusks as Dentalium, Fissurella, Patella, and 

 Spondylus. To me it appears that even this is only a secondary stage, and that the 

 primitive one was that in which the genital products, being discharged into the body- 

 cavity, were from thence con\-eyed outwards by the ciliated nephridium. 



This is, in fact, the arrangement as it still obtains in Proneomenia, and which is 

 most likely to be found in Chsetoderma and Neomenia as well. 



I will only add that the anatomical details, which we have just passed under 

 review, were none of them studied by direct macroscopic preparation. With 

 specimens of this rarity it seemed preferable to cut them iip into series of sections 

 which could all of them be preserved, afterwards reconstructing the original shape 

 by mental combination of the sections. This permits of aU the anatomical statements 

 being submitted to revision or criticism at any time, by the aid of the original 

 preparations. 



6. Report on the Migration of Birch. — See Reports, p. 189. 



6. On some Points in the Development o/Osmunda regalis (Linn.). 

 By Chas, p. Hoekirk, F.L.S. 



The object of this paper was to draw attention to the fact that Osmunda re- 

 fjalis requires six years to attain its normal development into the perfect spore- 

 bearing plant. The author showed dried specimens of the various stages of this 

 development, describing their details, and showing how each year produced a plant 

 gradually approaching towards the perfect form, and also exhibited a six-year-old 

 growing plant, producing spores for the first time. He also exhibited a portion of 

 a barren frond, in which some of the terminal pinnae were much constricted in 

 their development, and bearing spore-cases or thecre on their margins. 



X X 



