"LARVAE" OF CHIMERA. m 



intensified in the later stage, fig. 87. In fig. 88 the sac is still irregularly bilobed 

 and in figure 89, where it has been almost completely taken into the embryo, 

 the anterior lobe is still present. Observe in connection with these figures that the 

 shape of the sac is obviously correlated with the shape of the embryo inclosed 

 within the capsule.* A further consideration of these figures leads us to conclude 

 that in the latest stages of development the embryo of Callorhynchus rests on its 

 side, and in this position the dorsal fin is observed to lie neatly tucked against the 

 side of the body, the dermal web of the fin being folded under the depressed spine. 

 So also the paired and unpaired fins are closely apposed to the sides of the body, the 

 continuous dorsal and anal fins folding closely around the side. The dorsal fin folds 

 over the trunk towards the left side of the embryo. An outline of its margin, 

 slightly raised, is shown in fig. 86 A. In this stage the appearance of the frontal 

 clasping spine is indicated in fig. 86 B. This corresponds obviously to the con- 

 dition which is figured in a younger stage by Schauinsland in his Taf. xvi, fig. 122. 

 In Chimcera. The only late embryonic stage known to the writer is the one 

 preserved in the Jardin des Plantes and figured by Professor Vaillant in his 

 " Travailleur " report (1882), a specimen which the writer had the opportunity of 

 examining through the courtesy of its describer. This specimen (fig. 90 A, B), 

 probably of C. affinis, was dredged in the Bay of Biscay, together with fragments of 

 its egg-capsule. A small yolk-sac is adherent; this is of spherical form, and appears 

 to have been delicately connected with the body of the embryo. It is possible, 

 of course, that the present spherical form of the yolk-sac may have been the result 

 of the specimen having been freed from the capsule, for under this condition the 

 yolk-sac would probably have assumed its present shape. It may be noted that 

 the surface of the sac was deeply creased with blood-vessels, somewhat as indicated 

 in fig. 90 A. Noteworthy in this specimen is the great length of the hinder trunk 

 (and tail) which, it will be seen, is proportionately longer than in Chimara colliei, 

 and much longer than in Callorhynchus, and it is also to be mentioned that the 

 long urostyle shows that the continuous dorsal fin could not have extended function- 

 ally into this posterior region. Clasping organs are developed, and, as shown in 

 fig. 90 B, they attain even now a considerable size, about one-third their adult 

 (proportional) length. This condition is noteworthy as indicating again a precocious 

 type of development, sexual characters having been differentiated, although the 

 embryo is small in size and provided with a considerable yolk-sac. 



IMMATURE YOUNG. 



Four stages of "larvae" of Chimcsra colliei are shown in plates x and xi, to 

 illustrate especially changes in outward form, proportions, and coloration. The 

 specimens figured in plate x were secured by the Albatross during its work on the 

 Pacific coast, and were kindly placed at the writer's disposal by the United States 

 National Museum. The youngest specimen figured (fig. 51 and figs. 51* and b ) 

 was evidently lately hatched. It still shows the scar marking the point of intrusion 



*The irregular outline of the yolk-sac would, by analogy, probably be filled out if the living embryo were removed 

 from the constricting capsule. 



