PLaTeE 6. 
Development of Munemiopsis leidyi. Agassiz Laboratory, Newport, 
Rhode Island, July 27 to August 4, 1892. 
Fic. 20. Newly laid egg. 
Fic. 21. View of animal pole in a late segmentation stage. About 
6 hours after egg is laid. 
Fic. 22. Side view of stage slightly older than figure 21. 
Fic. 23. View of vegetal pole of an embryo about 7 hours old, slightly 
older than that shown in figure 22. 
Fic. 24. Side view of an embryo about 7 hours old. 
Fic. 25. First appearance of ciliary combs in 4 double rows. 
Fics. 26 and 27. Median sagittal optical sections to show arrangement 
of cells. Ectoderm dotted and composed of many small 
cells, individual cells not being shown in figure. Ento- 
derm cells large and drawn in outline. 
Fics. 28 and 29. Development of concretions at aboral pole of embryo. 
Figure 29 shows the same animal half-hour older than that 
shown in figure 28. Note remarkable development of 
cilia during the interval. 
Fics. 30-32. Oral, aboral, and side views of embryo about 3 hours 
older than those shown in figures 28 and 29. 
Fic. 33. Embryo still within the egg-envelope, about 24 hours old. 
No tentacles have yet developed. 
Fic. 34. Embryo with tentacles, about 30 hours old and still within 
the egg envelope. 
Fic. 35. Newly-hatched embryo about 30 hours old. The animal is 
now in the Cydippide-stage. 
Fic. 36. Aboral pole of an embryo about 32 hours old, showing de- 
cided lateral compression, the tentacular axis being now 
the wider, as in Mertensia, although the reverse is the case 
in the mature animal. 
Fic. 37. Side view of an embryo about 32 hours old, showing muscular 
strands. 
Fic. 38. About 36 hours old. View of aboral pole, showing a stage 
wherein the stomodzal axis has become nearly as wide as 
the tentacular. 
Fic. 39. Young Munemiopsis leidyi, 5 mm. long. The oral ends of the 
2 paragastric canals are now L-shaped, the 2 meridional 
ventral canals of each side are fusing at their oral ends. 
The tentacles are migrating downward toward the mouth 
and the oral lobes are about to develop. 
Drawn from life, by the author. 
