436 T. H. MORGAN. 



found. Here the ''split" is found over the broad surface of 

 one side, and not over the other. This condition is never 

 found in the falsely joined metameres of the Annelids, for even 

 in those cases where a metamere appears below, and not above, 

 it is also found to extend over and on one side (lateral) of the 

 body. 



Fig. 95, A, B, c, shows a spiral formed by a union of three 

 compound rings above and one below, as shown in the re- 

 construction. 



Fig. 93, A, B, c, shows a longer and more complicated spiral. 

 In the middle of this spiral we find a "double spiral" developed. 



Fig. 94, A,B,c, also shows a complicated spiral. These spirals 

 in the antennae are similar to the spirals found in the earth- 

 worm, and need no further description. 



The antennules of the lobster also show the same modifica- 

 tions. Both the antennae and the antennules are flattened 

 from above downwards, and the splits extend as a rule on the 

 lateral sides of the appendages. The basal joints of nearly all 

 antennae show imperfect rings. The greater number of abnor- 

 malities occur in the proximal portion of the antennae, and are 

 found in less and less frequency as far as the middle region. 

 They are rarely found in the distal ends of the antennae, and 

 it is important to notice that distally the rings become much 

 longer relatively to their breadth. Another interesting condi- 

 tion is found. By far the greater number of " splits " occur on 

 the convex side of the antennae and antennules, particularly in 

 the latter. There results a larger number of half-rings on the 

 convex side. In one case there were ten more half-rings on 

 the convex side of one antennule than on the opposite side. 



When we see that it is normal for the antennules to bend 

 outward, i. e. to turn their convex side towards the middle 

 line, it seems fair to draw the conclusion that the tendency of 

 the antennule to turn to one side is the direct or indirect 

 cause of the greater number of rings on the convex side. 

 There is no reason for believing that the greater number of 

 rings causes the turning, since the antenna is bent whether 

 more rings are present on one side or not. Processes that go 



