110 ME J. T. CUNNINGHAM ON THE 



not clearly shown. The eggs were hatched in May. The newly hatched larva 

 of Leuriscns rutilus is 6*5 mm. long, of L. idus, 73 mm. 



Fam. 4. Kneriid^e. 



„ 5. CHARACINIDiE. 



„ 6. CYPRINODONTIDiE. 



Many of the Cyprinodonts are viviparous. The males are always much 

 smaller than the females. A. Agassiz has figured some late stages of one 

 species, Fundulus nigrofasciatus, C. and V., but his youngest stage has the 

 homocercal tail already complete, and does not allow one to judge of the 

 characters of the newly hatched larva. 



Fam. 7. Heteropygii. 

 „ 8. Umbrid^e. 

 „ 9. scombresocidjl 



The position of this family is somewhat doubtful; it is placed by Gunther 

 among the Physostomi, although the air-bladder has no duct. By Claus 

 (Grundzuge der Zoologie, 4th ed., 1882), the family is added to the Anacanthini. 

 The peculiarities of the vitelline membrane in this family were first noticed and 

 described by Haeckel (Muller's Archiv, 1855). Prof. Kolliker, in the Verh. d. 

 Pln/sik u. Med. Ges. zu Wurzburg, 1858, corrected and added to Haeckel's 

 observations. A clear and satisfactory description of the membrane, with its 

 filamentous processes, is given by John A. Ryder, in his paper on the Develop- 

 ment oi Belone longirostris = Belone truncata, Gunther (Lesueur) (Bull. U. S. Fish 

 Commission, vol. i. 1881). From that paper we learn that the egg of Belone 

 is much heavier than sea water, and sinks rapidly to the bottom when un- 

 disturbed ; and also, that by means of the filaments, large numbers of the eggs 

 spawned from the same female are fastened together, and the clusters usually 

 become attached to foreign objects in the water, which objects may of course 

 chance to be either fixed or in a state of free suspension. The vitellus is 

 optically homogeneous, and the whole egg transparent, though, I infer, less so 

 than pelagic ova, The larva, after hatching, is not figured, but as far as can be 

 judged from figures of the embryo within the vitelline membrane, the anus is 

 in immediate proximity to the yolk. This point cannot be definitely decided. 

 The egg of Belone truncata is rather large, measuring, according to Ryder, 

 I inch diameter, or, as measured from the figure given by him, 3*49 mm. 



The vitelline membrane is provided with filaments similar to those of 

 Belone in the genera Scombresox, Hemirhamphus, and Exocoetus (flying fish). 

 Arrhamphus' eggs have not been examined. The eggs of Belone vulgaris, 



