310 Dr. O. vom Hath on the 



As regards the sense-organs of tlie Pliyllopods, e. g. Branclu- 

 ^nis, the views of autliors are divided. According to Leydig 

 [loc. cit.) and Spangcnberg *, two ganglion-cells, lying one 

 beh.ind the other, belong to each sensory hair; Clausf was 

 able to distinguish only one ganglion-cell ; in connexion with 

 the sensory hairs of Branchipus I always counted from three 

 to four cells, and from four to five beneath those of Apuft. 

 With the sensory hairs of both these Phyllopods I shall sub- 

 sequently deal at greater length. Among the Cladocera tlie 

 number of sense-cells belonging to each sensory hair is also 

 tolerably small. 



As regards the histological structure of tlie nerve-end appa- 

 ratus of the auditory organs, this in no way differs from the 

 description which I have given above. I am unable to con- 

 firm the statements of authors [e. g. Hensen, loc. cit.), who 

 ascribe only a single ganglion-cell to each auditory hair ; on 

 the contrary, I always found beneath the base of each auditory 

 hair of Astacus, Siriella, and Mi/ sis a distinct group of sense- 

 cells, with terminal cords reaching to the tip of the hair. 



I would here just mention in passing that behind tlie 

 groups cf sense-cells in the Crustacea I have never found those 

 peculiar large cells of glandular appearance, such as I have 

 described as companion cells (" Begleitzellen ") in the case of 

 the sense-organs of Myriapods and many Insects ; nevertheless 

 in the neighbourhood of the Crustacean dermal sense-organs 

 there occur, with a certain degree of regularity, on both pairs 

 of antenna, as well as on the whole of the limbs, irregular 

 groups of tyj)ical gland-cells, which are particularly noticeable 

 in the Amphipoda and Isopoda. 



instance perfectly acciu'ate." The latter remark is liable to be misunder- 

 stood. 1 therefore Liy stress upon the fact that Kiinckel is certainly in 

 error in holding tliat in luse; ts invariably only a single ganglion-cell 

 belongs to all sensory hairs. There are isolated cases, it is true, in which 

 only a single seustvcell is found in connexion with each sensory hair, and 

 I may refer the reader to my statements (Zeitj^chr. f. wiss. Zool. 4li Bd. 

 .'}, pp. 41G -411)) and figures (tigs. 3 b, 10, It!, 3l>). At that time I had not 

 included the sense-organs of the halteres vrithin the scope of my investi- 

 gations ; since then I have convinced myself by means ot series of sections 

 that it is actually true that only a single large bipolar ganglion-cell 

 belongs to each sense-organ. 



* Spangenberg, " Zur Kemitnis von Uranchipus staffnalis" Zeitschr. f. 

 •wiss. Zool. 25 Ikl. Suppl., 1875. 



t Clans, " ITntersuchungen iiber die Oi-ganieation uud Entwicklung von 

 lirandiiinis und Arfemia/' Arbeiten aus d. Zool. Institute d. Univ. \N'it.ii, 

 1885. 



