110 MR J. T. CUNNINGHAM ON THE 



formed a series of spots along the dorsal edge of the side of the body and tail. 

 This case is interesting, as showing how little modification is necessary to adapt 

 the ova of two allied fishes to such apparently different environments as the 

 surface of the sea and the bottom of a river or stream. The ova of the cod 

 sink in fresh water, but they probably would not develop in that condition. 

 The ova of Trigla gumardus sank in the water of the Scottish Marine Station, 

 but they invariably died in that condition after some days. The conditions in 

 which the ova undergo development are not constant in a given family, but the 

 structure of the ovum is more so, and the structure of the larva is alwavs 

 characteristic of families, and even, to some extent of whole orders. 



Fam. 3. Ophidiid.®. 



The eggs of Fierasfer {mm and dentatus) have been described by Emery in 

 his Naples Station monograph on the genus. The ovum has a single large oil 

 globule ; it is small. - 8 mm. in diameter. The ova when deposited are united 

 together in masses, each mass containing many thousand eggs in a thick gela- 

 tinous envelope. The masses are pelagic, floating at the surface of the sea. 

 In the newly hatched larva the anus is in immediate proximity to the yolk, 

 which still contains its oil globule situated at the anterior end. A great deal 

 of pigment along the sides of the trunk, and a single row of chromatophores 

 on each side at the ventral edge of the tail. A little in front of the level of the 

 anus a median dorsal papilla interrupts the continuity of the fin-fold. This 

 papilla grows rapidly, and ultimately forms a long filament supported on a 

 short upright stalk. The filament bears a number of leaf-like appendages, and 

 is called the vexillum. No stages of embryonic development are figured, and 

 in the figures of the larva the internal structure is not shown. The structure 

 of the notochord cannot be seen. A very lucid and complete account is given 

 of the ovarian development of the ovum. The vitelline nucleus is described, 

 and shown to be merely the starting point of the development of the vitelline 

 spheres, which by their coalescence form the yolk in the mature ovum. The 

 oil globule similarly arises from the coalescence of a number of small ones. 

 The differences in the structure of mature ova are thus explained, and no 

 support is given to the ideas recently advanced concerning the origin of the 

 yolk from follicular cells, or of the latter from the germinal vesicle. 



Fam. 4. Macrurid^e. 

 Development not yet studied. 



