ox THE DEVELOPMENT OF LIMULUS LOXGISPIXA. ^7 



Plate V. 



Fig. 1. Peculiar markings oii the shore, showing the place where eggs were laid. 

 Fig. 2. Surface view of an egg which has many irregular fissures (5 days after 



fertilization). 

 Fig. 3. Surface view of an egg with the blastodermic thickening (10 days after 



fertilization). 

 Fig. 4. Surface view of an egg, at the beginning of the metamerism (13 days 



after fertilization). 

 Fig. 5. Ventral surface view of an egg, 14 days after fertilization. 

 Fig. 0. The same as above, a little more advanced. 

 Fig. 7. Ventral surface view of an egg, 15 days after fertilization. 

 Fig. 8. Surface view of the ventral plate of an egg, at the commencement of the 



appearance of appendages (16 days after fertilization). 

 Fig. 0. The same as above, a little more advanced. 



Fig. 10. Surface view of the ventral plate of an egg, 17 days after fertilization. 

 Fig. 11. Two specimens of the chorion, broken up by growtli. 



Plate VI. 



Figs. 12-14. Three successive stages in the development of the ventral plate. 



The nervous system is marked dark red, while the mesoblastic somites are 



marked blue and the cavities in them light blue. Fig. 12, 19 days old ; 



fig. 13, 21 days ; fig. 14, 25 days, about x 30. 

 Fi-'. 15. Side view of an embryo, about 24 days old. 

 Fig. 10. Dorsal view of an embryo, about 25 days old. 

 Fig. 17. Dorsal view of an embryo of the trilobite stage, showing the formation of 



the dorsal circulatory system. 

 Fi". IB. Heart of Uiiniliis l'uhifhenuts, after A. Milne Edwards (much reduced). 

 Fig. I'J. Coxal gland of an embryo, about 27 days old, constructed from sections. 



a. Ventral view. b. Side view. 

 Fig. 20. Coxal gland of an embryo, about 30 days old, constructed from sections. 



a. Ventral view. b. Side view. 



