EMBEYOLOGICAL MONOGRAPHS. 



PLATE I. 



Development of Crixoidea (Comatula). 



Figures from C. 



GOETTE. 



'Wyville Thomson and Alexander 



1-9. Comatula, rosacea. From C. Wyville Thomson, On the Erabryogeny of Aatcdon rosacens Linck (Coma- 

 tula rosacea of Lamark), 1863. Trans. R. S. London, CLV., 1S65, Pis. XXIII. -XXVII. 



10- 26. Comatula medilcrranea. From Alexander Goette, Vergleicliemle Entwickclungsgeschiclite der Coma- 

 tula mediterranea, 1876, Pis. XXXV., X.XXVI. Archiv fiir Mieroskop. Anat., XII. 



27 -35. Comatula rosacea. From C. Wyville Thomson, On the Embryogeny of Antedon rosaceus, quoted above. 



1-9. Comatula rosacea. From C. Wyville Thomson. 



1. Egg shortly after impregnation. 



2, 3, 4, 5. Different st.iges of segmentation. 



6, 7. Development of the pseudembryo within the vitelline membrane. 



8, 9. Dorsal and ventral aspects of the pseudembryo sliortly before the disappearance of the ciliated bands. 



10-26. Comatula medilcrranea. From A. Goette, 



Oral funnel. 



Perisome. 



Circular canal. 



Plight peritoneal sac (aboral body cavity. ) 



Continuation of the same into tVie stem. 



.Stem of the young Comatula larva. 



Skeleton of the stem. 



Contractile tentacle. 



Non-contractile (rigid) tentacles. 



Visceral plate. 



Its continuation between the intestine and the 



water-system. 

 Water-system. 

 Stone canal. 

 Cords of vibratile cilia; 



10. Median section through a young larva (gastrula form). 



11. Median section through a somewhat older larva. 



12-15. Frontal sections of successively older larvip, seen from the dorsal side. 



16. Transverse section of a similar larva, anterior plane. 



17, 13. Sagittal sections; the median section is indicated in outline. 



19. Median sections of a somewhat older larva. 



20. Frontal section, seen from the ventral side ; the perisome begins to be intimately united with the outer skin 



and the parietal plate. 



