230 Prof. Dr. Fr. Vejdovsky on 



Sensory brushes are present on the telson * as well as on 

 the antennae, as has ah-eady been shown in many Amphipods. 

 Their position upon the surface of the telson appears to be 

 characteristic of the species of Nlphargus and Gammarus. 

 In Bathyonyx the telson is split for two-thirds of its length, 

 thus beino- bilobed posteriorly, the lobes gradually narrowing 

 and each being furnished at the point with a long and a short 

 simple seta (PI. XI. fig. 13). 



In addition there is always present here a short sensory 

 brush. Somewhat anterior to this group of hairs and towards 

 the exterior edge there are always two longer sensory brushes 

 of the same form and size as on the antennfe. The inner- 

 vation of all the sensory brushes on the telson evidently 

 proceeds from the lateral nerves of the last ventral nerve- 

 cord ganglion, as I have been able to demonstrate, for 

 examj)le, on the telson of the New Zealand species Cran- 

 yonyx compacfAis, Chilton. 



Quite different in structure from the sensory brushes are 

 the segmental sensory capsules, which, among different 

 Gammarids, exhibit a form typical for the genus. By means 

 of these sense-organs the genera Niphargus, Grangonyx, and 

 Gammarus can be determined with perfect safety. But tliey 

 are somewhat difficult to find, especially when only a few 

 occur on the segment, as they are characterized by their 

 extremely minute dimensions. It is only on this account 

 that 1 have not made an earlier reference to their occurrence 

 in Crangonyx. I refer to the capsules as segmental sense- 

 organs because they are distributed partly on the body- 

 segments and partly on the epimera. The form, number, 

 and distribution of the capsules can be seen without much 

 difficulty in preparations of the second epimera, where they 

 appear regularly disposed in a semicircle on the margin, and, 

 in consequence of the sharply contoured cuticular walls, they 

 stand out as plainly in the living animal as in preparations. 

 The sense-hairs, too, which are connected with the capsules, 

 make the recognition of tiie latter easier, 



Among the species of the genera already mentioned I have 

 made out the following forms of sensory capsules : — 



In Niphargus they are mostly flask-shaped, gradually 

 narrowing towards the exterior, where they pass into the little 

 sense-hair. The sense-hairs are mostly plumose, or like a 

 paint-brush, rarely simple and pointed. 



1 have examined the sensory capsules of various species of 



* Chilton has also observed tliem on tlie penultimate joint of the 

 Iburtli pereiopods in Gammarus fragilii^. 



