608 Bashford Dean Memorial Volume 



and paired fans show some development, and anal £n and lower lobe ot caudal are shown 

 in wavy outline. As one would expect by referring to Figure 33, plate III (the lateral 

 view), the dorsal and anal fins and lobes of the caudal are practically continuous. Along 

 the mid-ventral line is a ridge which I take to be the beginning of the tropeic folds. Note 

 how much like a tadpole the little fash appears. 



An EiiBRYO PLEASURING 55 Millimeters 



As noted above, Dean's "List" calls for drawings of the entire embryo and dorsal and 

 ventral views (presumably of the head) of an embryo of this size. These three drawings 

 I find, but, since they look old and are mounted on discolored cardboard, I conjecture that 

 they were made in Japan in 1901-02. They will be compared with the later-made draw- 

 ings of the 54-mm. specimen. The tull-length drawing ot the 55-mm. embryo in lateral 

 aspect measures 238 mm. ( = X 4.3+). 



Head Only. Dorsal View. — It is now m order to contrast the head (Figure 35, 

 plate III) of the 55-mm. embryo with the head of the 54-mm. specimen shovvTi in full 

 view in Figure 32, plate III. The 55-mm. head seems narrower but is rounded like the 

 other, the eyes are a little further forward, and the sensory-canal system shows very 

 indistinctly. The spiracles seem larger but show no gill-filaments. Nor are any filaments 

 visible in the widely separated gill-arches. One queries why the 54-mm. embryo has and 

 the 55-mm. one lacks these external filaments. Note that the pectoral fins of the 54-mm. 

 fish have little hook-like spaces between fin and body, while these are lacking in the older 

 embryo. In general it can be said that, contrasting the heads of two specimens, one gets 

 the impression that the 55-mm. head looks more finished — i.e., older. 



Full-length, Lateral Aspect. — The full-length lateral-view drawing of the 55-mm. 

 specimen (Figure 36, plate III) will be contrasted with the like drawing (Figure 33, plate 

 III) of the embryo of 54-mm. Naturally the differences between them are individual 

 rather than of stages of development. The original dravdng of the 55-mm. fish measures 

 238 mm . (i.e., X4.3— ), that of the 54-mm. one measures 257 mm. (i.e., x4.7-r)- In the 

 55-mm. embryo, head and trunk are straight above and the head rounds off forwardly to 

 a rather distinct snout. The nasal apertures are situated well forward almost in their 

 definitive position. The lower jaw is not so long as that of the 54-mm. embryo. The 

 lateral-line system show^s plainly on the trunk but on the head is hardly so well-developed. 

 The gill-covers (especially the first) are also hardly so w^ell developed and the external 

 filaments are not nearly so long as those in the 54-mm. fish. The spiracle of the 55-mm. 

 specimen is higher on the head and contains several short gill-filaments. Ot the fins, 

 pectorals, pelvics and dorsal are about equally developed in both embryos. The anal fin is 

 better developed and more sharply marked off from the lower lobe of the caudal in the 

 55-mm. embryo. The caudal fin droops, whereas that of the 54-mm. fish swings upward. 

 Unfortunately the artist has used dark lines to indicate some grooves between somites, 

 which thus appear like branches of the lateral-line canal. 



Head Only, Ventral View. — Perhaps most instructive will be a comparison of the 

 under surfaces of the two heads — the 55-mm. specimen in Figure 37, plate III, and 



