148 



Proceedings of the Royal Physical Society 



Bilateral symmetry, which is such a characteristic feature of the 

 Crustacea, is seeu in the arrangement of the additional genital openings in 

 41 of these 45 abnormal examples. The presence of the characteristic modifi- 



FiG.p. Genital Apertures of Nephrops norvegicus. 



Male of Nephrops norvegicus with abnormal genital apertures on the third pair 

 of walking legs. 



cation of the anterior abdominal appendages, as in the male Nephrops, 

 establishes the sex of the solitary example with apertures on the third and 

 fifth pairs of walking legs (Text- fig. 1). The abnormality here shown is a 

 very interesting one, and I have not been able to find another record of a 

 similar example. 



