15'J MKKISTIC VARIATION. [PART I. 



\'iirinttn in (lie n timber of generative openings in Crayfishes. 



Astacus fluviatilis. A female having the normal pair of 

 o\ iducal openings on tin- bases of the antepenultimate pair of 

 walking legs. ami in addition to them another pair of similar 

 opening- placed njmii tin- corresponding joints of the penultimate 

 pair of walking legs. <>n dissection it was found that the ovary 

 ua- normal, and that from each side of it a normal oviduct was 

 given off; Inn each of tip-.- oviducts divided a little lower down 

 to (MIIII two Hnaller oviducts, one of which went to each of the 

 four oviducal openings. 1 )i>\iA iirsT 1 , E., Ann. Soc. Ent. France, 

 1848, Ser. _'. vi. p. 47!. /'/. 



Astacus fluviatilis $, having a supernumerary pair of ovi- 

 ducal opening placed mi tin' luxt pair of thoracic legs. The normal 

 oviducal openings wen- in the usual position and of the usual 

 shape and si/e. but in addition to them there was an extra pair 

 placed on the last thoracic legs. It should be remarked that 

 though the-e are the appendages upon which the openings of the 

 male organs are placed, the oviducal openings were not in this 

 case -ituated at the posterior surface of the joint as the male 

 op, nin-- are, but were placed relatively to the leg in the same 

 situation ax the female openings on the antepenultimate legs. The 

 penultimate legs and the abdominal appendages were normal. On 

 dissection it was found that each oviduct after passing for the 

 greater part of its course as a single tube, divided into two parts, 

 one of which went to each oviducal opening. The ovary itself 

 was normal. HiiMi \M. \V. B., Ann. M<I : /. .V. //.. ]s!)l, Ser. 6, VII. 

 p. '2't>\. /'/. ill. ! I am ui'catly obliged to Mr Beiiham for an oppor- 

 tunity of examining this specimen. Attention is called to the 

 tact that in this specimen Homoaosis occurs in an unusual way, 

 having a gap in the series: for the openings are on the ante- 

 j unlfiimitf and fnxt thoracic legs respectively.] 



I tesmarest's observat ion stood apparently alone until lately, when 

 the specimen jusl described and several others presenting the same 

 or -imilar variations were observed by I'.KNiiAM. Mr Benham was 

 kind enough to ^ ml me the following specimens for examination: 

 one female having a xiii<ilc r.rfrn oviducal opening on the left side 

 upon the penultimate thoracic leg (Fig. 2(JC), and two females 

 having a similar extra opening in the same place on the right 

 ( Fig. :><i. ]i); in both of bhese the normal oviducal openings were 

 unchanged. Together with these Mr llenham also sent a female 

 haxing in, It/ ,,,!< oviducal opening on the right side and another 

 having ,,/,/ tin- ii-ft oviducal opening (Fig. '20. A ), the correspond- 

 in^ leg of the other >ide having no trace of an opening. 



r liinl tlii- -] riiiH-ii frnin r<n--;srAr (/. c., p. 481 note): Faxon 



tin- i-:is.- !//,//;. Hull., vni. i iici-id. -ntally n-i<u'si-nts it as two cases, but the 



ii'-ti- t.i Deemarett'fl jopri >h, - that tli.' (lisrnptiun referred to a single specimen 

 only. 



