100 



digging, the majority of them were sitting obliquely in the sand, only 

 half buried, the darker posterior end being above the sand. In places they 

 were found so close together that they were touching one another, some- 

 times over several square meters. They were found to be ripe in May — 

 June, and fertilization was undertaken on May 29th. The egg is sur- 

 rounded by a mucilaginous coat with purple pigment spots. About the 

 first developmental processes I have omitted to make any notices. The 

 embryos had assumed the shape of small Plutei at the age of two days. 

 In eight days old larvae the first indication of the metamorphosis (formation 

 of the amnion) was found; none of the specimens, however, developed 

 through metamorphosis; but, anyhow, the full larval shape was reached. 

 The shape of the larva (PI. XIV, Figs. 5 — 6) is very much like that of 

 Echinarachnius parma (comp. especially PI. VII, Fig. 1 of Fewkes' paper 

 on the development of that species^)). The arms are rather narrow, not 

 widened at the base ; they have all of them a prominent red pigment spot 

 at the point, while the larva is otherwise without color. (A noticeable 

 fact is that it turns green when preserved in alcohol; this fact was ob- 

 served also in several other Clypeastroid larvae and probably will prove 

 to hold good for all of them, in accordance with the fact that Clypeastroids 

 upon the whole generally turn green when preserved in alcohol ; also when 

 otherwise damaged the tissue on the damaged place turns green 2)). The 

 posterodorsal rods have their lower ends connected by a muscular band 

 and are thus movable; the same holds good for the postoral arms in the 

 later stage, when the lower part of the body skeleton has been absorbed. 

 — On the sides of the anal lobe the vibratile band makes a downward 

 curve, thus forming a pair of small vibratile lobes; a corresponding pair 

 of lobes is found on the dorsal side and also on the side of the body the 

 band forms a pair of small, posterolateral lobes. As seen in the figures 

 there is an indication of a ciliated band going from the corner of the 

 preoral band obliquely downwards towards the band along the dorsal 

 side. This band, which I have also observed in other Clypeastroid larvae 

 (and which is also seen in the larva of Echinocyamus pusillus, comp. PI. VI, 

 fig. 90 of Theel's Monograph), is probably a special feature of the Clypea- 

 stroid larvae and may have something to do with the oral nervous system 

 occurring in the Echinocyamus-laryai and probably in Clypeastroid larv« 

 in general (comp. p. 71); but this needs a closer investigation. — The 

 esophagus shows an indication of the structure observed in the larva of 



J I. W. Fewkes. Preliminary observations on the development of Ophiopholis and 

 Echinarachnius. Bull. Mus. Comp. Zool. Harvard Coll. XII. 4. 1886 



• '^ Some interesting observations on this remarkable property of Clypeastroid tissues are 

 given by W. I Crozier m a paper "On the pigmentation of a Clypeastroid Mellita sesqui- 

 perforatus (sicl) Leske". American Naturalist, Vol. LII. 1918. p. 553. 



