Genital Apertures in the Norway Lobster. 



147 



2. Examples with Three Genital Openings. 



154 individuals show the abnormality of a single spermatic opening in 

 addition to the normal two. This is the most common form of variation as 

 regards the genital pores. The additional aperture is found on the right or 

 left leg of the third or fourth pair of walking legs. This gives a series of 

 four different arrangements, which may be represented more clearly in the 

 following manner : — 



Walking Legs. 



R. 1 L. 



R. L. 



R. L. 



R. L. 





Third Pair 



Fourth Pair . . 



Fifth Paii- 



• 



• 



• 



• 



2 





Total Num. of Examples 



77 



72 



3 



= 154 



It will be noted that variation occurs here without any regard to symmetry. 

 In five of these examples there are no openings on the fourth pair of legs, 

 while these occur on the third and fifth pairs. There is thus a gap in the 

 series of openings in the segments, a good example of what Bateson calls 

 homoeotic variation as distinguished from purely meristic variation. 



3. Examples with Four Genital Openings. 



This form of variation is found in 45 examples. As in the previous case, 

 the additional apertures are found on the third and fourth pairs of walking 

 legs. The different arrangements observed are the following four : — 



Walking Legs. 



R. 1 L. 



R. L. 



R. L. 



R. L. 





Third Pair 

 Fourth Pair 

 Fifth Paii- 



• * 



• 

 • 



• 



• 



• * 





Total Num. of Examples 



40 



2 



2 



i 



= 45 



1 R. and L. stand for Ri"ht and Left sides. 



