146 THE ARMED BULL-HEAD FAMILY. 



condition being represented in Plate VI, fig. 1. As they get a 

 little older their length seems to diminish rather than increase, 

 and the black chromatophores occur on the cheeks. The bases 

 of the breast-fins show rows of them springing from the distal 

 edge of the basal process. The fin-rays everywhere are still 

 embryonic. The sides of the body from the tips of the breast- 

 fins backward almost to the tail show a series of isolated black 

 chromatophores arranged in a double row, viz. towards the 

 dorsal and the ventral edges. A gronp of similar pigment- 

 specks characterises the median or wider part of the marginal 

 fin dorsally and ventrally (region of the dorsal and the anal fin). 

 On the sides and ventral surface of the abdomen the same 

 black corpuscles are scattered, and they run along the ventral 

 surface to the base of the tail. A slight narrowing — dorsally 

 and ventrally — is evident in front of the tail, which likewise 

 has only embryonic rays. The vent is very prominent, and in 

 front of it another projection occurs— a feature characteristic 

 of this form. The notochord (rudimentary back -bone) is quite 

 straight. 



When 6 mm. in length (in spirit), and thus shorter than the 

 larval form, as in the case of the paradoxical frog of North 

 America, a great change occurs in regard to the surface, e.g. on 

 the 19th April. The fish is now considerably broader and 

 thicker, and more densely pigmented on the ventral than the 

 dorsal surface, as in the di'agonet and other forms, and some 

 specks also are evident behind the breast-fins. Rows of sharp 

 and slightly curved spines pass along the dorsum, on the lateral 

 crests of the head and on the gill-covers. True rays appear on 

 the lower part of the tail, besides a basal thickening (hypurals); 

 and permanent rays are also developing in the breast-fins. 



When about 8 mm. long, as in the end of April and 

 beginning of May, the head has now acquired a predominance in 

 bulk — from its elevated dorsal (occipital) and ocular ridges, its 

 spines on the gill-cover, and a tendency to the occurrence of 

 tubercles generally. The spines on the trunk and abdomen 

 are prominent. All these are much more developed in propor- 

 tion than in the adult. Slight papillae on the chin mark the 

 future ' cilia.' The head is boldly differentiated from the 



