614 Bashford Dean Memorial V^olume 



25". Among them is a specimen of 205 mm. This I judged to be the specimen drawn 

 and I concluded that it was dra\^m in natural size since the embryo of Figure 11, plate I 

 measures 205 mm. around the curves. Furthermore, it seemed that a yolk sac 92 x 90 mm. 

 would not be too large for an embryo of this size. But the figure bears in Dean's writing 

 the notation "175" and the last embryo of the seven taken "April 25" is Hsted as "175" 

 mm. So it seems clear that, in the original drawing, the 175'mm. embryo and yolk sac 

 are enlarged 1.2 times. There is no drawing of the 205 -mm. embryo. 



Seen from Above. — The only embryo with which to compare this I75'mm. specimen 

 (Figure II, plate I) is that of 124'mm. and of it the drav.nng of the head only (Figure 44, 

 plate IV). The head of the 175'mm. fish looks distinctly older even though the remnants 

 of external gill-filaments show in the arches. In contrast, the snout of the Httle I75'mm. 

 fish is blunter than that of the 124'mm. embryo, the eyes far less prominent, and the gill- 

 covers far less spread out. The presence of gill-filaments even though small, is not un' 

 usual since they are found in far older specimens as will be seen later. The pectoral and 

 pelvic fins have a decidedly '"growTi up" appearance. Dorsal and anal fins are well de- 

 veloped and the lower lobe of the caudal looks very much Hke that of an adult. The tip 

 of the caudal is bent downward and is devoid of a notch. The lateral-line system is 

 clearly marked, and the latero-sensory canals and ampullae on the head are well delineated. 

 On the trunk region, the lateral-line grooves appear to be connected across the dorsum 

 by transverse broken lines drawTi in white. These are like those shown in the tail-region 

 of the 55-mm. embryo (Figure 36, plate III). They are surely inter-somitic grooves, not 

 portions of the lateral-line system. This portrayal (Figure 11, plate I) shows the vitelline 

 circulation in an advanced stage of development. It will be considered shortly. Alto- 

 gether this is the most artistic drawing thus far found. 



i\s" Embryo 185 mm. k Length 



Dean's "List" calls next for an embryo of 185 mm. to be drawn full-length in lateral 

 aspect without yolk. This drawing is reproduced herein as Figure 46, plate IV. The 

 original drav.Tng measures 185 mm., hence is natural size — the first of the embryos so 

 draum. This little fish looks very like an adult even though it was attached to the yolk 

 sac by a yolk cord measuring 11 mm. in diameter. To see how tar this embryo has 

 progressed, it must be compared with the 124-mm. specimen (Figure 45, plate IV), 

 seen in the same aspect. (The 175'mm. embryo cannot be used in comparison, since it 

 is portrayed in dorsal aspect, and is moreover not drawn straight). The snout ot the 

 185'mm. fishlet is more pointed ( dorsO'ventrally compressed); nasal capsule and eye are in 

 their normal positions. The long lower jaw brings the mouth almost to the terminal 

 position. The gill-flaps are nearly as normal as those of the fine 124'mm. embryo, which 

 lacks the remnants of gill-filaments present in the 185-mm. fish. The body is humped 

 and on it is a well-developed lateral line with latero'sensory branches on the side ot the 

 head, and v.^th marked bends under the dorsal fin. Above the lateral line, the artist has 

 inserted broken lines as if they were branches of the lateral Hne. They are spaced to 

 correspond with the grooves between the myotomes immediately ventral to the lateral 



