172 University of California Publications. [Zoology 



1893, and as through an accident most of these were lost, a brief 

 description of it was all that was published at that time. 



The observations made and material collected during the past 

 summer enable us now to materially increase our information 

 about this tornaria, so far as the later larval and earlier metamor- 

 phosing stages are concerned. Unfortunately, however, it was 

 impossible, with the aquarium facilities possessed by the lab- 

 oratory, to carry the metamorphosis through the later stages. 

 We are, conseqently, obliged to leave some of the developmental 

 questions that are in most urgent need of re-examination, 

 practically untouched. Furthermore the earliest larval stages, 

 upon the study of which the answers to several important 

 questions of euteropneust development depend, did not occur in 

 the tow. 



What we now present on the structure of this larva is of 

 interest rather from the ecological point of view, to which we 

 have especially directed our attention, than from the morphol- 

 ogical and developmental standpoint. 



The most notable fact in connection with the distribution of 

 the species during the season was its almost constant absence 

 from the surface waters, and its equally constant occm-rence at 

 a depth of from twenty-five to one hundred fathoms. So far as 

 we have definite records in only a single instance were specimens 

 taken during the summer in the surface gatherings, while most 

 of the hauls in depths as indicated above, over the "banks" (to 

 be described later) , at least with the large plankton net, secured 

 specimens. It must be borne in mind, however, that closing 

 nets were not used, and consequently that there was always the 

 possibility that specimens came from the surface even when they 

 were present in hauls from the depths. The evidence we have 

 that they were taken below the surface is the fact that surface 

 towings made simultaneously or nearly so in almost all eases 

 secured none. But this evidence is sufficient to justify the con- 

 clusion that the larva 3 were much more abundant at depths 

 ranging from twenty-five to one hundred fathoms than at the 

 surface. Another noteworthy probability relative to the distri- 

 bution afforded by the season's collecting is that the parents of 

 the larvae were not living in the littoral zone, but on the "banks" 



