38 SUMMARY OF CURRENT RESEARCHES RELATING TO 



than the other, the genital region becomes visible as a whitish spot with 

 the female opening clearly marked, and, after a series of convulsive 

 movements, the spirillum amoris is ejected with a final exhausting effort. 

 It was once observed that both snails discharged their darts simul- 

 taneously, and this is said to be normal in H. nemoralis. The dart 

 usually penetrates the margin of the foot, and the immediate effect of it 

 is to cause increased excitement in the other snail, ending usually in the 

 expulsion of its dart also. This phase may last for a couple of hours, 

 and is followed by a long resting period. In the final stage the position 

 and movements are similar, the genital tract is again prominent, and 

 both male and female apertures are clearly visible. Many unsuccessful 

 attempts may be made before the proper relative position, and the 

 simultaneous extrusion of the organs have been attained, and the sper- 

 matophore of each snail is safely deposited in the receptaculum of the 

 other. Slowly the snails disengage themselves, the genital region is 

 retracted, the head slightly drawn in, but the undulatory movements of 

 the foot continue, and the snails remain together for tw T o or three hours 

 until the terminal threads of the sperrnatophores, which still connect the 

 two, are entirely drawn in. During the whole process the snails are 

 quite indifferent to external circumstances. Moving them about, or 

 turning a strong light upon them did not distract them in the least. It 

 occasionally happened that three snails met together and united in the 

 most manifold combinations. Which two ultimately succeeded in pairing 

 depended simply on the chances of position ; there was no hint of any- 

 thing like selection. 



Some time later the snail hollows out a passage leading down to a 

 roomy chamber in the ground, and, hanging head downwards through 

 this passage, drops the eggs one by one on the floor of the chamber, 

 smooths over the top of their hiding-place, and leaves them to develop. 



The second part of the paper deals with the morphology and physi- 

 ology of the reproductive organs. The histology of the dart-sac and the 

 mucous glands, and their relation to each other are described in detail. 

 The extrusion of the dart is preceded by the outpouring of a considerable 

 quantity of fluid from the glands. The author differs from v. Ihering 

 and others in that he regards this fluid merely as a lubricant which 

 facilitates the expulsion of the dart, and possibly also the entrance of the 

 penis into the vagina. The spermatophore is an exact cast of the rele- 

 vant male organs, due to the solidifying of the secretion of the flagellum, 

 which is poured out just before and during the passage of the sperms 

 from the vas deferens. The thick head part with its longitudinal ridges 

 represents the anterior part of the penis, while the terminal thread corre- 

 sponds exactly to the lumen of the flagellum itself. The spermatophore 

 is formed just before and during copulation. The observer did not 

 succeed in actually tracing the course of the spermatozoa to the upper 

 end of the oviduct, where, within a diverticulum — the " fertilisation- 

 sac " — the eggs are fertilised. He found numerous spermatozoa within 

 the hermaphrodite duct, and these were in no way distinguishable from 

 those — presumably from another animal — in the fertilisation-sac itself. 

 The question as to their relative immaturity, as suggested by Perez, was 

 not investigated. 



