8 MK. F. H. A. MARSHALL OIs' [Jan. 14, 



of Man lobsters may point to the percentage being related to the 

 locality ^. 



The positions of the additional openings upon their respective 

 legs are approximately the same as those of the normal ones on 

 the fifth legs. In the case of those specimens with three pairs of 

 openings, the most anterior of which are situated on the third 

 legs in the position of oviducal openings, it is clear, if only from 

 the modification of the anterior abdominal appendages, that the 

 specimens are males. The abnormal apertures are sometimes 

 smaller than the normal ones, though they may be even larger. 

 In the case of the single specimen showing seven spermatic 

 apertures, the six posterior openings are of about equal size, 

 while the opening on the second thoracic leg on the left side is 

 very much smaller but still quite obvious. 



The state of preservation of the majority of the specimens 

 rendered it impossible to determine the structure of the internal 

 genital organs. In the fresh specimens it coidd, however, in some 

 cases be made out that the apertures opened internally into blind 

 sacs. In a few there appeared to be duct-like extensions of these 

 sacs internally. In a fair proportion the vasa deferentia gave 

 ofi" branches which extended for a short distance towards the 

 abnormal openings. In at least one instance these anterior forks 

 of the vasa deferentia reached the bases of the legs on which the 

 abnormal apertures were situated. Whether there is ever a free 

 functional passage from the position of the forking to the 

 abnormal aperture it is difficult to say with certainty. 



That Norway lobsters with additional genital apertures have 

 been common in Scottish waters for a considerable number of 

 years, appears from information supplied me by Professor Ewart, 

 Dr. Beard, Dr. Masterman, and others. Before I began my 

 investigation on the degree of frequency of such abnormal 

 lobsters, Dr. Masterman expressed the opinion that quite 10 per 

 cent, of the specimens he had observed since he had been in 

 Scotland had additional genital openings ; and Dr. Beard, who 

 has had occasion to examine a very large number, speaks to me 

 of regTilar epidemics of this kind of abnormality in some years 

 in the past, the students in the laboratory experiencing gi-eat 

 difiiculty in distinguishing the males from the females. 



The only published record, so far as I know, of additional 

 genital openings in JVephrops is a recent paper by Mr. Cole, who 

 states that " abnormalities in oviducal and spermatic apertures 

 are by no means uncommon, and I remember examining three 

 specimens, two of which were abnormal and had four super- 

 numerary spermatic apertures occurring as follows : — 

 Third walking-legs. • 



• • Fourth walking-legs. • 



• • Fifth walking-legs. • • " 



1 Mr. Bateson infonns me that he has noticed some variation in the degree of 

 frequency of ahuormality in regard to the oviducal apertures in batches of Astacns 

 procured at various times for the Zoological Laboratory at Cambridge, and is of 

 opinion that this variation is probably related to the localities from which the 

 batches were obtained. 



