138 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 



., . , Number of 

 T 1 Number of tj„,i:_i 



l-egular. otoliths. ^X. 



7, 6, 7; 7, 7, 8; 8; 1,8; 20, 8; . . 5, 1 forking. 



9, 6, 8; 27; 8, 11; 3 3 



6, 5, 6 ; 7, 7, 5 ; 5, 3 ; 2, 3 ; 5, 5, G ; . 8 5 



7,6,5; 7,8; 1, ,10; 14; . . . 5 4 



2, 3, 3; 3, 1,3, 4; 1,3,2; 2, 8, 4; . 9 4 



6, 6, 7; 6, 15; 6, 2; 1,8, 6; . . . . 6 4 



On Plate IX. will be found a number of diagrammatic figures giving 

 an idea of the irregular growth of the marginal tentacles. The lengths 

 of the tentacles are drawn as fully expanded, the position of the radial 

 and circular canals is indicated, and the otolith tentacles are marked by 

 a cross. The structure and length of the marginal tentacles of Eucope 

 are such that the comparative length of adjoining tentacles is readily 

 observed, owing to the slight degree of contraction and expansion they 

 possess. 



In Figures 1 to 6, 10, and 14 (Plate IX.), we have the normal num- 

 ber of tentacles (seven) in each of the primary quadrantic subdivisions. 

 It is noticeable that fi can only in the case of Figures 4 and 10 be dis- 

 tinguished from the two to, while the four t^ are of nearly uniform size 

 in all the figures except Figure 6. 



In Figures 7, 12, 13, 16, 17 (one primary division), 18, 19, and 22- 

 26, there are only five niarginal tentacles in each primary quadrantic 

 division. In the gi-eater number of these figures it is possible to dis- 

 tinguish ^1, or ti and t2, while the irregularly developed tentacles are 

 part of the ^3 cycle. In Figures 20-22 (one sector), and 27-29 (two 

 sectors), the cycles ti and <2 c^" be distinguished, and the irregular- 

 ity of development occurs in the ^g cycle, which may appear at different 

 points of the circular canal, as is seen by comparing Figures 20-22, 27, 



and 28. 



Figures 8-10, 17, 22, 29, and .30 show the irregularity in time of the 



development of the marginal tentacles in the different sectors of the same 



quadrant, as well as the irregularity in the growth of the three cycles 



ti-t^ in adjoining sectors. In Figures 8, 29, and 30, the marginal 



tentacles between the otoliths are in the same stage of growth, but 



the tentacles of the right or left sectors are in very different stages of 



growth. In one case (Fig. 30) only one t^ is developed in each sector ; 



in Figure 29 the cycles of ti and to are normal, while they are most 



irregular in the sectors of Figure 8. 



When six marginal tentacles occur in one sector the irregularities in 



