2 Dr. W. G. Ride wood on a Case oj 



In Nephrops it is no uncommon circumstance for additional 

 genital apertures to be present. F. H. A. Marshall*, 

 writing in 1901, records how, on an examination of 1000 

 male specimens, he found 12'2 per cent, abnormal in having 

 supernumerary genital openings, and more recently I). C. 

 M'lntosh t examined 44:29 males, and found that 287 were 



Yis. 1. 



a-- 



Ventral view of the bases of the last three thoracic legs, a, aperture on 

 the base of the third leg on the right side ; b and c, the apertures 

 on the fourth and fifth legs on the left side. Two-third.s natural size. 



abnormal, a percentage of G"5. In none of these specimens 

 were the usual ducts on the last pair of walking-legs wanting, 

 ihe abnormality invariably consisted in the occurrence of 

 genital ducts in addition to the normal pair. These speci- 

 mens were caught in the Firth of Forth and Moray Firth. 

 Of 319 males captured in the Clyde, M'lntosh found 2"5 per 

 cent, to be abnormal in having supernumerary genital 

 openings. In no female specimen examined by him was 

 any abnormality observed, either in the position or the 

 number of the apertures, a truly remarkable circumstance in 

 view of the large percentage of abnormal cases among the 

 males. Marshall J, however, mentions one case in which, in 

 addition to the normal oviducal openings on the third or 

 antepenultimate walking-legs, there were a pair of apertures 

 on the last walking-legs. 



M'lntosh makes no mention of the manner in which the 



* Marshall, F. II. A., Proc. Zool. Soc. Lond. 1902, i. pp. 2-12. 

 t M'lntosh, U. C, Proc. Roy. Physical Soc. Edinb. xvii. 4, 1908, 

 pp. 129-142. 

 + L. e. p. 0. 



