654 BASHFOED DEAN, 



Larva of about the thirty-fiftli day (PL 11, Fig. 25; 

 ventral aspect PI. 11, Fig. 26). 



This stage, the latest to be figured in the present paper, has 

 acquired the main outward features of the adult. The fins suggest 

 clearly their mature forms; the intervening membranes of the larval 

 unpaired fins have become greatly reduced, c-a., that of the pre-anal 

 abdominal region having entirely disappeared ; the definitive caudal, c, 

 has now supplanted the larval caudal, and leaves it reduced to the 

 condition of urostyle, u., entirely separated anteriorly from the pos- 

 terior margin of the dorsal. The outline of the mature ventral fin 

 is now attained, and its basal portion suggested. In all fins dermal 

 rays, d. r., have made their appearance at the distal ends of the 

 radials ; to these their ontogenetic relations have not been determined, 

 nor yet their subsequent outgrowth, and formation of splits and 

 joints. In the entire trunk region the appearance of scales may now 

 be noted although they have their greatest prominence in the region 

 of the lateral line: unlike in Lepidosteus they do not exhibit 

 cusp like outgrowths: they at once attain their oblong shape and 

 their growth suggests closely that of the Teleost. The head growth 

 is marked by the general outmapping of the dermal bones of the 

 cranial roof, and by the definiteness of those of the opercular and 

 orbital regions. To these, however, the relations of the mucous canals 

 are as yet simple; for the subsequent growth of the mucous canals 

 cf. Allis. The jugular plate, jug.^ has now its characteristic position 

 and proportions. 



III. Notes on organogeiiy. 



The general form-changes in the larval Ämia have been briefly 

 reviewed in the foregoing pages. Notes on several of the more ira- 

 portant features of larval organogeny may now be added, derived 

 from a study of serial sections: i. e., a) Mouth, teeth, gullet, swim 

 bladder; b) anus, postanal gut, ncurenteric canal, hinder excretory 

 ducts; c) liver, yolk; d) pronephros; e) brain, neuromeres, hypophysis ; 

 f) sense organs, sucking organ, ciliation. 



a) Mouth, teeth, gullet, swim-bladder. 

 The formation of the mouth in Ämia differs little from that in 

 Lepidosteus, Sturgeon and in Teleosts generally, The stomodaeum 

 establishes its opening into the fore-gut earlier than in other Ganoids, 



