256 



Fig. 3. Echinopluteus transversus, species f. Ventral view. The vibratile band not distinct 

 over the Echinoid-rudiment. 85 /i- 



4. Same larva as fig. 3, in dorsal view. 85 /i- 



5. Young larva of Mellila sexiesperforata (Leske); 24 hours old. Ventral view. lfo /,. 



6. Larva of same species, same age; side view. 



Plate XIV. 



Fig. 1. Young larva of Layamim iliplopora H.L.Clark; 3 days old. Ventral view. 200 /i. 



2. Embryo of Clypeaster japonicus Doderl., 2V 4 days old. Showing beginning forma- 

 tion of the skeleton. 180 / 1 . 



3. Larva of same species, 11 days old. Ventral view. Drawn from life. 145 / 1 . 



4. Gastrula of Echinarachnius mirabilis (A. Ag.), 18 hours old. 180 /,. 



5. Fully developed larva of Echinarachnius (Dendrasler) excenlricus (Esch.), 14 days 

 old. Ventral view. From a preserved specimen, combined with a sketch from a 

 living specimen. Skeleton dissolved. 105 / 1 . 



6. Larva of same species, same age: side view. Slightly restored. 105 /i- 



7. Larva of Encope micropora Ag., 14 days old: ventral view. From a preserved spec- 

 imen, combined with a sketch from a living specimen. 150 /,. 



Plate XV. 



All figures of Peronella Lesueuri (Val.). Figs. 1 4 drawn from life, 85 /, ; the rest 180 /,. 

 Fig. 1. Embryo, five hours old, in the blastula-stage; showing irregular folding of the ecto- 

 derm. 



2. Young larva, 17 hours old. The mouth has been formed, and the postoral arms 

 are beginning to appear as a pair of small lateral thickenings. 



3. Young larva, 20 hours old: dorsal view. The postoral arms are distinct. 



4. Fully formed larva, 39 hours old: ventral view. The preoral lobe has been completely 

 reduced, the mouth opening now being at the anterior edge of the body. 



5. Longitudinal section of an embryo, 9 hours old. A number of mesenchyme cells 

 have been formed, but gastrulation has not yet begun. 



C. Longitudinal section of an embryo, 12 hours old. Gastrulation has begun. 

 7 10. From a series of longitudinal sections of an embryo, 16 hours old; showing 

 the shape of the entoderm. Between figs. 7 and 8 there is one section, fig. 9 following 

 immediately after 8; there are 3 sections between figs. 9 and 10. 



11 13. From another series of longitudinal sections of an embryo, 16 hours old; showing 

 the shape of the entoderm. Fig. 11 is the more dorsal of the three. In fig. 13 is seen 

 the apical thickening. 



14. Longitudinal, sagittal section of an embryo, 16 hours old. The mouth (in) has begun 

 to form. 



15 18. From a series of frontal, longitudinal sections of an embryo, 18 20 hours old. 

 Fig. 15, which is the more dorsal of them, shows the widening (am.) from the lower 

 end of the pharynx (ph.), surrounding the entoderm (ent.); this widening gradually 

 disappears in the following figures. In fig. 18 is seen the rectum (r) in a lateral posi- 

 tion. There are 4 sections between figs. 15 and 16, 1 between figs. 16 and 17 and 

 4 sections between figs. 17 and 18. 



19 22. From a series of sagittal longitudinal sections of an embryo, 18 20 hours old. 

 Showing the posterior prolongation (am.) from the pharynx (ph.). Also the shape 

 of the archenteron (ent.) appears from a comparison of these figures. Fig. 20 shows 

 the blastoporus, which has now shifted to the ventral side, to form the anal open- 

 ing (a). 



Plate XVI. 



All figures of Peronella Lesueuri (Val.); all 18 %- 



Fig. 1. Longitudinal, frontal section of a larva 23 24 hours old. Showing the amniotic 

 prolongation (am.) of the pharynx (ph.) continuing to the posterior end of the body. 

 The part in the middle is the raised ventral wall of Hie amnion (romp. figs. 1 1 1(>): 



