574 
J. S. KINGSLEY. 
Fig. 6. — “ Germinal disc ” of embryo after the appearance of the eighth 
(first gill-bearing) appendage {ga v ). The distinction between the cephalo- 
thoracic and abdominal regions is now distinct. Osmic acid preparation; 
camera drawing. 
Figs. 7 and 8. — Surface and sectional views of deutovum after separation 
from the embryo. X 160. 
Fig. 9. — Diagrammatic upper and. Fig. 10, side views of segmental organ, 
constructed from sections. I am not certain about the internal termination, 
f. Cf. Fig. 27. 
Fig. 11. — Embryo at the time of moulting. The second larval cuticle {ci) 
viewed obliquely from the front to show the procephalic lobes {pc). 
Fig. 12. — Embryo at the time it escapes from the chorion and assumes a 
Limuloid appearance. The position of the eye (e), extending across a meso- 
blastic partition, is noticeable. 
Fig. 13. — Horizontal section of an embryo of the stage shown in Fig. 14, 
taken above the level of the eyes, to show the extent of ingrowth of the 
mesoblastic partitions {mp). x 14. 
Fig. 14. — Under surface at the “trilobite stage,” constructed from camera 
drawings. Owing to difficulties of manipulation the brain could not be seen, 
and the metastoma may not be correct. 
Fig. 15. — Reproduction of Metschnikoff’s figure (’71, PI- xvi, fig. 12). “A 
part of the embryo [of Scorpio] to show the first formation of the lung.” 
p. ab. Abdominal appendage, pn. Pulmonary sac. 
Fig. 16. — Dorsal and, Fig. 17, ventral views of young Limulus at the 
escape from the deutovum and beginning of a free life. X 14. 
Figs. 18, 19, and 20. — Diagrams illustrating the derivation of the pulmonary 
sacs of the Arachnids from the branchiae of Limulus. 
Fig. 18. A single gill-appendage with the gill-lamellae, as shown in the 
adult Limulus. 
Fig. 19. The gill-appendage is partially sunk in the ventral surface, and 
the gill-lamellae exhibit a condition shown in Figs. 37 and 38. 
Fig. 20. Diagram of pulmonary sac of an Arachnid. The gill-lamellae 
are replaced by the pulmonary lamellae ; the pit of invagination has 
narrowed above and foims a spiracle. 
