OF ARTS AND SCIENCES. 279 



greatly increased in length since the stage of Plate XI. fig. 5. The 

 caudal rays are edged with rows of narrow pigment cells, while in 

 the preceding younger stage the pigment spots of the caudal were 

 limited to the base of the rays (Plate X. figs. 3, 4), or there are but a 

 few irregularly scattered along the fin rays (Plate X. fig. 5). There 

 is a marked line of pigment cells along the base of the dorsal and 

 anal ; in the anal an additional line of pigment spots runs near the 

 outer edge of the fins. The general coloring of this stage approaches 

 quite nearly that of the adult, though the body and the lateral line do 

 not have quite as silvery a lustre as in the older stages. 



In the oldest Atherina here figured the snout has become quite 

 pointed (Plate XI. fig. 7). The anterior dorsal has made its appear- 

 ance, the caudal is forked, the dorsal and anal are high, having much 

 the shape they have in the adult, the pectorals are quite pointed. 

 The permanent rays of all the fins are now edged with narrow pig- 

 ment cells. The pigment spots of the lateral line consist of three or 

 four irregular lines of minute dendritic chromatophores, while the 

 dorsal line is made up of two irregular lines of large spots extending 

 from the snout to the base of the tail. The ventral line extends only 

 from a point slightly in advance of the base of the anal to the caudal 

 fin ; it also consists, like the dorsal line, of two irregular lines of 

 elongated jjigment spots. In this stage the young Atherina has fairly 

 assumed the principal characteristic features of the adult. 



Batrachus tau, Lin. 

 (Plate XVI. fig. 1.) 



Dr. Storer has given a figure of a young Batrachus (Mem. Amer. 

 Acad, v., Plate XIX.) measuring about 2""" in length. It differs but 

 slightly from the large specimens, the more rounded outline of the 

 head, as seen from above, and the greater elongation of the head 

 characterising this younger stage. 



A young specimen (Plate XVI. fig. 1), measuring only 8""™ in 

 length, was slender, the pectorals fully developed ; the openings in 

 the mucous membrane of the head were well developed, the ven 

 trals small ; the dorsal and anal fins were still connected with the 

 embryonic caudal, the separation between the anal and caudal being 

 but little marked. The tail fin was still in an embryonic stage, with a 

 well-marked trace of the ganoid lobe. The whole fish was dotted with 

 small i)igment spots, with a few larger cells scattered irregularly over 



