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Transactions. 



spermatozoa arise and develop in this follicle. Here are found spermatozoa 

 in all stages of development, and when mature they pass from the follicle 

 by means of an efferent duct to the main hermaphrodite duct. The outer 

 follicles discharge their ova into the central one, and the ova thus reach the 

 hermaphrodite duct in the same way (fig. 7 ; c/, ej.d, x). These ducts of the 

 hermaphrodite gland are all ciliated. In the region of the seminal vesicle 

 the dorsal side of the hermaphrodite duct loses its cilia, and becomes differ- 

 entiated into a glandular structure of a beautiful rich dark brown. The cells 

 of this gland are very large, and each contains a yellow secretion, which is 

 distributed throughout the whole cell. In my sections of this region I found 

 the lumen completely blocked up with spermatozoa. 



There is no sharply marked-off albumen-gland discharging into the 

 common duct, as in the case of Aplysia and Helix, but the common duct 



is itself very glandular, the posterior 

 end especially ; and the glandular 

 walls of this duct, which become 

 much folded, as we shall see, consti- 

 tute the albumen-gland, so that the 

 albumen-gland appears to form part 

 of the duct in the reproductive system 

 of Sifhonaria ohliquata. The lumen 

 of this region of the duct is very com- 

 phcated, and for the purpose of fol- 

 lowing out its anatomy I cut a series 

 of sections through the whole of the 

 duct, and by a study of these have 

 been able to arrive at certain conclusions, which I propose to discuss in 

 another paper. 



The eggs are deposited in a gelatinous material round the base of the 

 mollusc, and are left attached to the rock in more or less circular ribbon - 

 hke masses (fig. 8). There are several eggs enclosed in each shell. 



Fig. 8. — Gelatinous ^Iibbon-like Mass 



CONTAINING EgGS. 



Represented a.s deposited by Siphonaria. 



NOTE,S ON PRESERVING, ETC. 



For preserving my specimens for dissection I used both formol and 

 alcohol. The former has the advantage of preserving the natural colours, 

 and this fact is especially useful in studying the nerve-collar, the ganglionic 

 masses being orange-coloured. However, formol renders the tissues. Math 

 one exception, very hard ; this exception is the glandular region of the 

 common duct. In formol specimens I found this to swell up and become 

 very brittle, so as to make it almost impossible to dissect. This organ 

 preserves better in alcohol, and my drawings are frgm spirit specimens. 



I tried several methods of killing Siphonaria so as to get the specimen 

 well distended. I found this end was accomplished best by leaving freshly 

 collected specimens for four or five days in a dish mth a little sea-water 

 in the bottom, then getting them gradually into fresh water, and thence 

 into spirit or formol. 



For fixing the tissues for histological purposes I used corrosive subli- 

 mate, corrosive sublimate plus 5 per cent, acetic acid, and glacial acetic 

 acid. With all I obtained good results, but where I was able to make a 

 fair comparison between them I found that in the majority of my prepara- 

 tions the last reagent gave me the best results. 



