OP ARTS AND SCIENCES. 285 



permanent dorsal appendages of Lophius, which are eventually changed 

 to the appendages used for fishing by the adult. What part this tem- 

 porary dorsal appendage plays in Fierasfer is not known, but Emery 

 supposes it to have the same function as in Lophius. 



COTTUS GRCENLANDICUS, C. Sf V. 



(Plate III., Plate II. figs. 1, 2.) 



The eggs of this species (Plate III. fig. 1) are found floating on the 

 surface ; they are readily recognized from the number of small oil 

 globules (from 10-12) wliich the yolk contains. Other Cottoids lay 

 their eggs in bunches attached to the bottom, or singly between stones 

 in shallow water. The young immediately on hatching (Plate III. 

 fig. 2) are characterized by the great width of the anterior part of the 

 body, the breadth of the embryonic dorsal fin toward the head, and the 

 great size of the fleshy pectorals. Viewed from above, when slightly 

 older (Plate III. fig. 3), the pectorals are seen to project far beyond 

 the general outline as thick fleshy flaps ; their formation as a fold of 

 the primitive lateral "embryonic fold is well shown in the stages within 

 the egg (Plate III. flg. la Ic) ; in the last stage (Plate III. fig. Ic) 

 they appear to stand independently of the body upon the yolk mass. 

 In the stages of Plate III. figs. 4, 5, the rapid increase in the size 

 of the head and of the pectorals can be traced. In the stage of 

 Plate III. fig. 4, the permanent pectoral fin rays are commencing to 

 form, and in Plate III. fig. 5, what we may call the crossopterygian 

 stage of the pectorg,ls is very striking. 



The development of the anterior part of the body goes on, as in 

 Lumpus, much more rapidly than that of the posterior, and at a stage 

 (Plate II. fig. 1) where the Cottoid characters of the head and pecto- 

 rals are already very striking, the embryonic dorsal and anal folds are 

 still united with the caudal fold, and the tail only shows, as yet, a 

 rudimentary caudal fin and the beginning of the ventrals. 



In the nexl; stage (Plate II. fig. 2) the spiny processes of the 

 operculum and head of the young Cottus are well developed, and the 

 pectorals fins have all the appearance of that of older specimens ; 

 the ventrals are well advanced, the dorsals and anals are separated 

 from the caudal fin, the permanent fin rays are quite prominent, and 

 the anterior dorsal exists as a Ioav fin. 



The general coloring of this stage of the young Cottus is of a dirty 

 yellowish brown, with patches of darker pigment cells and black spots 



