﻿142 Proceedings of the Royal Physical Society. 



up to six apertures, though Dr Marshall found a single 

 example with seven openings. The eleventh and twelfth 

 columns of Table VI. show how continuous is the series when 

 account is taken of the number of openings, irrespective 

 of their arrangement. The absence of symmetry in both 

 arrangement and number is very marked. No correlation 

 could be traced between the number of genital apertures and 

 any organ. It is desirable to discuss the nature and origin 

 of these additional openings in a separate paper. 



The conclusions may now be summarised as follows : — 



1. That the occurrence of additional genital apertures 



is by no means uncommon (Table IV.). 



2. That the abnormal genital openings occur without 



any regard to bilateral symmetry (Table V.). 



3. That, as one would expect, the number of examples 



showing abnormality decreases as the extent of 

 the abnormality increases (Table VI., columns 11, 

 12, and 13). 



It remains for me to give my best thanks to Professor J. 

 Cossar Ewart and to Dr Ashworth for their kindness in 

 allowing me to examine the stock of Norway lobsters in 

 the Zoological Laboratory of Edinburgh University, and 

 for granting facilities for the working up of the data; to 

 Dr Marshall, of the Physiological Department of Edinburgh 

 University, at whose suggestion the inquiry was originally 

 begun ; and to Mr Alexander Bowman, B.Sc, of the scientific 

 staff of the North Sea Investigation International Board, 

 who has not only supplied me with much material, but has 

 assisted me in arranging the various data. 



