197 



in the right posterior corner. The larva is colourless, excepting lor a slight 

 yellowish tint along the vibratile band. The larval nervous system was not 

 distinctly observed. 



Stichopus Kefersteinii Selenka. 



Of the rather numerous Holothurians occurring along the rocky shores 

 of Taboga. in the Bay of Panama, several species were found to contain 

 ripe sexual products in October — November 1915; many attempts were 

 made to obtain their larva' through artificial fertilization, but the results 

 were very poor. With the present species a fertilizalion was undertaken 

 on October 23rd, which resulted in a small number of embryos. At the age 

 of two days these latter were beginning to assume the Auricularia-shape; 

 on the 3rd day all the embryos had died. A number of specimens were 

 examined in order to have started a new culture, but all were empty by 

 this time. The information acquired about the development of this species 

 accordingly does not go beyond the fact that it has a typical pelagic larva. 



Holothuria n. sp. ('?)') 



PI. VI, Figs. 5 — 6. 



Like the preceding species this one was found to contain ripe sexual 

 products in October; fertilization was undertaken on the 21st of this month 

 1915. The eggs were found to ripen after lying about 3 hours in the water; 

 they then readily accepted the spermatozoa and quite a large percentage 

 w'as fertilized. The cleavage is perfectly regular; the gastrula-stage was 

 reached at the age of one day, and at the age of two days the embryos 

 showed the beginning formation of the Auricularia. Three days old they 

 were typical young Auricularias of the characteristic shape shown in PI. 

 VI, Fig. 5, with the anterior part very broad, almost bell-shaped. At the 

 age of 8 days the larvae had reached the stage shown in PI. VI, Fig. 6. 

 On the dorsal side the vibratile band now almost joins in the midline in 

 the anterior end; otherwise the larval shape is still quite simple, without 

 any indication of processes. The frontal area may perhaps be somewhat 



') Tliis a|)prars lo l)c an uiulosiTihed s|H'i'ies, allii'd lo H. Lapiotania' Hi'll. It may be 

 shortly thus characterized: Lengtii 5- -6 cm. Dorsal side brown, wilii two rows of small, 

 black spots; ventral side pale; tentacles yellow. Deposits in the skin: slightly curved, very 

 spinous rods; well developed end-plates in the pedicels. Calcareous ring high, without a deep 

 notcii posteriorly, (lenital tuft h)ng; only one Polian vesicle. 'I'lie madreporite is single, 

 fastened on the mesentery, with lancctshaped head; the stone canal is s-shapetl. (Uivierian 

 organs present. Locality: laboga, Ciulf of Panama. Littoral. 



I am indebted to Miss E. Deichmann for the above remarks on this species. 



In the list of the F.chinoderms the development of which has been studied in the i)resent 

 work, given in the Introiluction (p. 17 --18), this species was forgotten. 



