LARVAE OF DECAPOD CRUSTACEA 



By Robert Gurney, D.Sc. 

 (Text-figs. 1-42) 



INTRODUCTION 



THE collection of decapod larvae from the Discovery plankton is so large that it 

 seems hardly possible to deal with it as a whole. It has occupied a great deal of my 

 time for several years, but much remains to be done, and it has seemed best to simplify 

 the task a little by reporting upon sections of the material without regard to systematic 

 order. 



Although these collections contain an astonishing variety of larval forms, many of 

 which are of great interest, the proportion of early to late stages is remarkably small, 

 and it is consequently rarely possible to fit together any complete series of stages. The 

 material is particularly rich in larvae of very large size, but very small larvae are hardly 

 represented at all. Even among the Sergestidae, for example, although mastigopus 

 stages abound, elaphocaris and acanthosoma stages are rare, and of Lucifer I have seen 

 larvae in one sample only. 



The majority of plankton samples were taken far out at sea, a fact which may account 

 for the absence of early stages of littoral species, but not for those of the many deep-sea 

 forms of Caridea. 



PART I. STENOPIDEA 



Such knowledge as we have of the development of Stenopus is derived from the work 

 of Brooks and Herrick (1891) and of Cano (1892) on S. hispidus and S. spinosus re- 

 spectively. Brooks and Herrick were able to study the larva hatched from the egg, so 

 that the characters of this first stage are established with certainty, but none of the later 

 stages described belonged to Stenopus at all (Gurney, 1924, p. 133). Cano did not state 

 by what means he identified his larvae, but there is no reason to doubt that they belonged 

 to Stenopus, and he was able to describe a series of stages leading to a larva of very large 

 size which was later met with by Ortmann and described under the name of Embryocaris 

 stylicauda (1893). 



I am indebted to Dr J. F. G. Wheeler for specimens of Stenopus hispidus hatched 

 from the egg at Bermuda, and have included a description of this stage, since Brooks 

 and Herrick's account is not quite clear in some particulars. These specimens also 

 •enable me to correct an error in the series of stages which I described in 1924. I then 

 regarded as stages I and II two larvae which were taken together in one sample and 

 were assumed to belong to one species. It is now clear that the specimen referred to 

 stage I belongs to quite a different species, later stages of which are found in the 

 Discovery material. In this material there are no small stages, but an embarrassing 

 number of different forms, no less than nine being distinguishable. 



