388 WILSON. 



EXPLANATION OF PLATE XVL 

 {Esperella fibrexilis.) 



Fig. 20'". The ovarian egg of Fig. 20'", with neighboring tissue. D.4. 



Fig. 21. Gemmule breaking up or " segmenting." Section. D.4. 



Fig. 22. Section through a gemmule near the close of "segmentation." D.4. 



Fig. 23. Part of a section through a gemmule, entirely broken up into 

 separate cells. D.4. 



Fig. 24. Longitudinal section through gemmule, in which the posterior pole 

 is differentiating. C.4. 



Fig. 25. Longitudinal section through gemmule larva, still in body of parent. 

 C.4. 



Fig. 26. Surface view of swimming larva shortly after birth. A. 4. 



Fig. 27. Surface view of swimming larva 36 hours after birth. A. 4. 



Fig. 28. Surface view of incompletely metamorphosed larva. A.4. 



Fig. 29. Longitudinal section of larva shortly after birth. D.4. 



Fig. 30. Longitudinal section of older larva. D.4. 



Fig. 31. Ectoderm cells of swimming larva — maceration products. 



■ maceration products. 



