127 



To this same larval type further belongs the larva of Ophiothrix angu- 

 lata Say (Var. poicila 11. 1.. Clark), which I succeeded in reariiii* durini> 

 my stay al Tobago, 1!. W. I. in April 1916. Ripe specimens of Ibis s|)ecies 

 were secured on A|)ril 11th, which gave o IT sperm and eggs; the eggs were 

 shed all al tbesanu' lime, almost as by an explosion. The first development 

 processes pass veiy much in accordance with what is know'u Ironi (). fra- 

 gilis. M the age of 18 hours the embryos were found to be lenticular in 

 shape, but still without skeleton. Al the age of 21 hours they were already 

 snudl plulei with fairly long posterolateral arms, the other arms not yet 

 having appeared (corresponding to the stage represented in PI. 31. Fig. 6 



Fifi. ."),'{. Ski'li'lon ol' ( )jihi()phiteus of Ophiothrix. sjx'cics a. -'"/,. 



of MacBri(le"s memoir on Die developmenl of Opiiiolliri.i jnujilis '), wliich 

 is, however, much older, 55 hours). At the age of 40 hours the postoral 

 and anterolateral rods had begun lo form, the corresponding arms being 

 as yel merely indicated, while the posterolateral arms are already of con- 

 siderable length; their rods are still without thorns. The larva in tliis stage 

 is exceedingly characteristic, the preoral and jjostoral band continuing 

 almost straight across the anterior edge of Ihe body (PI. XX, Fig. 1). Al 

 the age of 4^2 days the larvae had reached nearly their full shape, only the 

 inner arms not having attained their full length (PI. XX, Mg. 2). I'horns 

 had begun lo appear on Ihe jjosterolateral lods: the median process from 

 the transverse rods had nol yet been formed. .\ small group of red pig- 

 ment grains is found near the base of the posterolaleral arms, and there 



iiu'iuiin^i was, of rouiso. lluit il is iiniiossihlc to decide to which species it belonus, as it coidd 

 hardly lie doul)ted that it must belong to some species of the i-eiuis Ophiothrix. 



In the "Kchinodermenlarvcn d. deutsehen SUdpolar-Expedition" (1913 p. il8) this larva 

 was recorded from olT Ascension. 



') Quart. .lourn. Micr. Science. Vol. .'il. 1907. 



