300 Dr. O. vom Rath on the 



Insects*; the following paper is intended to give the most 

 important of the results which I have obtained from the 

 Crustacea. In addition to studying our indigenous fresh- 

 water Crustacea f and land Isopods, I availed myself of the 

 opportunity afforded by a sojourn at the Zoological Station at 

 Naples to investigate a large number of marine forms belonging 

 to all the orders and families of which I was able to obtain 

 specimens. My object in so doing was, by comparative 

 studies, both to elucidate the morphology of the several 

 sense-organs, as well as to determine as thoroughly as possible, 

 by means of scries of sections, the finer structure of tlie nerve- 

 end apparatus belonging thereto ; for I am of the opinion that 

 an exact knowledge of these relationships is a necessary con- 

 dition for rational physiological experiments, and that many 

 of the interesting attempts which have been made to determine 

 the function of the sense-organs situated on various parts of 

 the body are not conclusive because sufhcient regard has not 

 been paid to other sense-organs of a similar kind. 



In the copious literature of the Crustacea we find, as we 

 are all aware, a large number of valuable statements as to 

 individual sense-organs, which, however, in reference to the 

 nerve-end apparatus are not unfrequently contradictory. The 

 reason for these conflicting interpretations may for the most 

 part be found in the fact that very few authors have examined 

 the sense-organs in question by means of sections, and that 

 in examining even the transparent forms confusion may easily 

 take place between the nuclei of the true percipient sense- 

 cells and those of the epidermis-cells. It would be out of 

 place in this short essay to enter into the literature of the 

 subject, yet I would at least recall the important writings of 

 Leydig, Claus, Weismann, Leuckart, La Valette, Hensen, 

 Sars, Hoek, liougemont, Wrz^sniowsky, Gamroth, Haller, 

 Blanc, and Krae])elin. To Leydig the merit is indisputably 

 due of having first described the most important dermal 

 sense-organs in Crustaceans, Myriapods, and Insects. 



In the following pages only the most general results of my 

 investigations will be given as briefly as possible : I intend 



' * 0. vom Rath, " Pie Sinnesorgane iler Auteiine mid dor I'uterlippe 

 der Cliilogiiathen," Arcliiv f. niikr. Aiiat. '21 15d. 1880; " Ueber die 

 llaulsinne-sorgaDe der lusecteii,'' Zoitschr. f. wiss. Zoologie, 4ii IW. 

 3 Heft, 1888. 



t Among the higher Crustacea I have jiaid special atteution to Astaciis 

 fiuridti/iK, and have examined tlie wliole of its dermal seuse-orgnns ; as 

 the hardness of the chitiii jiresents great dilhculties to the scali.el, I 

 emphiyed fur the purposes of dissection as far ns possible specimens 

 wlui'h liad just luoultcd mul wit.' still fairly .-iift. 



