THE STOMATOPODA. 317 



The eggs of the ordinary Edriophthalmia usually undergo 

 their development in the chamber beneath the thorax inclosed 

 by the oostegites of the thoracic appendages. In most cases, 

 the young differ so little from the adults that no metamorpho- 

 sis can be said to take place. They frequently, however, 

 want the last thoracic somite. The young of the parasitic 

 Edriophthalmia^ such as Bopyrus, Phryxns, Cymothoa, Cy- 

 amiis, and the Hyperinm, on the other hand, are widely dif- 

 ferent from the adults ; and not only in their metamorphosis, 

 but in the small proportional size and less aberrant form of 

 the male, Bopyrus and Phryxus recall the parasitic Cope- 

 poda. 



In certain Amphipods (Gammarus locasta and Desmo- 

 philus) the vitellus undergoes complete division ; w T hile, in 

 closely allied forms (Gammarus fluviatilis and pulex), and 

 still more completely in those Isopoda which have been 

 studied, the part of the vitellus which divides into blasto- 

 meres becomes more or less completely separated from the 

 rest immediately after fecundation, and the so-called partial 

 yelk division, take place. 1 



In all Edriophthalmia, the development of which has 

 been examined, before any other organs appear, a cuticular 

 investment or sac is formed, which is eventually burst and 

 thrown off. This appears to represent the Nauplms cuticle 

 of 3Iysis, and, in close relation with it, are peculiar tergal 

 structures, such as the bifid lamella? of Asellus, and the un- 

 fortunately named "micropyle apparatus" of other Edrioph- 

 thalmia. 



The Edriophthalmia are not abundant in the fossil state ; 

 but they may be traced back as far as the later Palaeozoic 

 strata (Prosoponiscus, Amphipeltis). 



The Stomatopoda. — Of the Stomatopoda of Milne-Ed- 

 wards, two of the three divisions, the Carido'ides and the 

 Bicuirass'es, have since found a place among the Schizopod- 

 ous Podophthalmia, or among the larvae of certain Macra- 

 ra; but the third, the Stomatopodes unicuirass'es, compris- 

 ing Squilla, Gonodactylus, and Coronis, appear to me to differ 

 so widely and in such important structural peculiarities, not 

 only from the Podophthalmia proper, but from all other 

 Crustacea, as to require arrangement in a separate group, 

 for which the title of Stomatopoda may well be retained. 



1 E. van Beneden, " Recherches sur la Composition et la Signification de 

 l'CEuf," 1870. 



