THE SUCKER FAMILY. 198 



notochord (primitive back -bone) is quite straight to the tip, and 

 its cells are large. The heart has a small oil-globule below it, 

 and the large oil-globule lies immediately behind the heart — in 

 front of the granular yolk. No blood-vessel occurs in the tail 

 proper, the aorta passing almost to the tip of the notochord, 

 and bending upward and forward into the vein. Such larval 

 forms as just described are very common in the nets from 

 March to May, clusters of eggs and ripe females being especially 

 abundant during the former mouth and April. Post-larval 

 forms, again, of .5-5 to 6*5 mm. (in spirit) occur in April, and in 

 some it would appear as if the body were somewhat shortened 

 in the post-larval condition. 



In May also the larval Montagu's suckers are frequent, with 

 various older stages up to 11 mm., the beautiful pigment of the 

 breast-fins being very characteristic (Plate VII, fig. 9). Mr 

 Holt found similar forms during the survey off the west coast 

 of Ireland, the smaller forms being translucent in the fresh 

 condition. In spirit those of 11 mm. have the dorsum and 

 sides minutely dotted with black points, and the breast-fins are 

 finely pigmented. A considerable number of specks also occur 

 on the under surface. In life, however, the fish is translucent, 

 the dots being very minute, only those on the breast-fins 

 attracting notice by the regularity of their arrangement. The 

 dorsal fin shows an anterior differentiation of four rays, as if a 

 first dorsal were indicated, the region immediately succeeding 

 having shorter rays. In this connection it is curious that the 

 adult male American examples have the first six rays prolonged 

 and fleshy. There are 29 rays in all, and the fin is connected 

 with the tail. The larval tail — with its hair-like embryonic 

 rays and the sloping notochord — is still present. The anal fin 

 has 24 rays, and, like the dorsal, is joined to the tail. The 

 pectoral has 30 rays, and the pelvic fins 6 rays, so that in these, 

 as in the other forms, the rays agree with those of the average 

 adult — with a full number of rays. Such forms are met with 

 not only in inshore, but occasionally in offshore waters. 



Examples during June are few, but several post-larval forms 

 6 mm. long have been obtained. These — probably in a sickly 

 condition in the tow-net — form the prey of jelly-fishes like 



M. F. 13 



