ISO TAOK SKOr.SIlKHr. 



situatod on tho anterior odgo, ono medially, somewhat anteriorly ;iii(l one on the posterior edge 

 of the joint. Of these tliree bristles the first-mentioned is relatively short or of moderate length 

 and of about the same type as the bristles on tlie third, fourth and the original sixth joints; 

 the two other bristles are generally of about the same type as each other, typical sensory bristles, 

 rather powerfully annulated proxiraallv, more and more finely aiiiudated distally, near the point 

 sometimes even (juite hyaline, characterized by simple, fine sensory filaments, generally of 

 about the .same thickness throughout their whole length, situated dorsally and distributed 

 fairly etjually along the greater part of tlie length of the bristles. Like the distal part of the 

 principal bristles these sensory filaments are very finely annidated or even (juite hyaline; in 

 addition, like the principal bristles they are finely rounded distally and furnished there with 

 a short, fine sensory hair. Tiie one of these bri,stles that is situated medially, somewhat anteriorly, 

 is of moderate length and fitted with relatively few sensory filaments; exceptionally, for instance 

 Cypridina (Ciipridinn) serrata (G. W\ MtlLLER) var. affirmans, ?, (cf. the description of this 

 form, given below) it is even quite without any appendages; the posterior one of these bristles is 

 comparatively long and furnished with a relatively large number of filaments. The small 

 (original) end joint has four bristles. Two of these, situated close to each other distally-laterally 

 on the joint, are of quite the same type, narrow or moderately thick, distally roimded sensory 

 filaments, of about the same thickness throughout; proximally they have ratlier powerful 

 annulation, distally with increasingly close and fine annulatiou or more or less completely 

 hyaline; both are quite naked. The remaining two bristles, both comparatively long, are of 

 about the same type as the posterior bristle on the preceding joint; they both issue distally- 

 mediallv, one a little in front of the other. 



Male: — Often more extended than that of the female. The sensory bristle of the 

 fifth joint is developed in about the same way as in the female, with exactly the same or else 

 with only an insignificantly larger number of sensory filaments. Of the bristles of the original 

 seventh joint the posterior and the one placed distally-medially and somewhat anteriorly are, 

 in almost all genera so far known (exception: Crossophoms), furnished with suctorial organs 

 for seizing the female. (These suctorial discs were interpreted by G. 0. Sahs, 1887, p. 39, as 

 sensory organs — he writes: ,,et eiendommeligt Mart, baegerformet Appendix, aabenbart of 

 sensorisk Natur"* — a view which has, however, not been accepted by succeeding writers. 

 It had already been interpreted correctly by C. ClaUS, 1873, p. 221.) The different genera 

 vary not inconsiderably with regard to the type, number and arrangement of these suctorial 

 organs. As in the females the two bristles in <[uestion differ from each other in their length; 

 the one that is situated distally-medially and somewhat anteriorly is comparatively short in 

 this sex as well, the other is long. Sometimes the bristles of the seventh and eighth joints are 

 of about the same length in males and females, sometimes two or three of them are more or less 

 lengthened in the former sex. This lengthening is found in different bristles in different forms; 

 in some forms the posterior bristle on the original seventh joint and the anterior one of the 

 two distal-medial bristles of the eighth joint are lengthened, in others it is both the distal-medial 

 bristles of the eighth joint and in others all these three bristles. 



* Translation: „A peculiar hyaline, cup-shaped appendix, evidently of sensorial iiaturf "' 



