117 



It should still be mentioned that in some of the young larvae the ento- 

 derm was everted, turning inside out. Some of these abnormal larvae were 

 isolated in order to see what would become of them. They partly assumed 

 the normal shape again, the entoderm being again invaginated, and after- 

 wards developed normally, being only somewhat delayed in their devel- 

 opment, so that at the age of five days they were at a stage of develop- 

 ment corresponding to that of two days age in the normal larvae. These 

 belated larvae otherwise showed the very interesting feature of having a 

 distinct vibratile band (Fig. 48), which was never observed in any of the 

 normal larvae. 



Echinobrissus (Oligopodia) recens (M. Edw.). 



PI. XI, Figs. 4—5. 



On my visit to New Zealand I was, of course, very anxious to get an 

 opportunity of studying the development of this interesting Echinoid, 

 which is known with certainty to occur only in New Zealand waters. It 

 was not met with on the trip with the "Hinemoa" (comp. above p. 62). 

 On my return to Wellington I then made (on the 16th of February) a 

 little dredging trip from there, the species being known to occur in the 

 neighbourhood, as it is sometimes found washed up on the beach there. 

 After some unsuccessful attempts in the Cooks Strait I had the pleasure 

 of finding some few (9) adult specimens and also some young ones in the 

 entrance to Wellington Harbour at a depth of ca. 10 — 12 meters on a 

 fairly coarse gravelly bottom. They proved to be nearly empty all of them, 

 but fortunately a few females still contained some eggs in good condition, 

 and also a ripe male was found so that it was possible 

 to undertake fertilization, which proved successful. 



The eggs are surrounded by a very peculiar mem- 

 brane, whieh appears concentrically stratified ; the inner 

 layers are following the outline of the cleavage cells, 

 while the outer ones remain spherical (Fig. 49). I am 

 not sure, whether this is the fertilization membrane or Fig. 49. Egg in dea- 

 lt is also found in the unfertilized egg, corresponding ^^g^ oi Echinobrissus 



°°' '^ ° recens, showing the 



to the mucilaginous coat of the Clypeastroid eggs. (The peculiar membrane. 

 fertilization was undertaken somewhat late in the even- After a free hand 

 ing, at the Zoological Laboratory of the Victoria College, 

 where the material from the dredging was taken. Professor H. B. Kirk 

 kindly lending me every assistance). .On account of the late hour it was 

 also impossible to follow the cleavage process, only the two-cell stage being 

 observed. At the age of ca. 24 hours the embryos were in the gastrula stage, 

 and on the second day they were beginning to assume the Pluteus-shape. 



