STOMATOPODA. 297 



11, Stomatopoda. 



The Stomatopoda are a branch of the higher Crustacea which 

 very early separated from the common Malacostracan stock, and 

 whicli retain in their organisation very primitive features, side by 

 side with peculiar developmental forms. Among the former we 

 may reckon the long dorsal heart provided with many pairs of 

 ostia, and the condition of the dorsal shield which covers the 

 segments carrying the maxillipedes, but does not fuse with them. 

 Another primitive character is perhaps found in the presence of ten 

 pairs of segmentally-arranged hepatic tubes, some of which belong 

 to the abdomen. The position of the more important organs (hepatic 

 tubes, genital organs, heart) in the large abdomen is a distinctive 

 characteristic of the Stomatopoda, as opposed to other Malacostraca, 

 in which this region of the body serves almost exclusively as a 

 muscular locomotory organ. 



On the other hand, the metamorphosis of the Stomatopoda shows 

 peculiar characters, although it cannot be denied that it has a 

 certain ontogenetic tendency in the same direction as that of other 

 Malacostraca. In spite of the important treatises of Claus (No. 86) 

 and Brooks (Nos. 83 and 84), our knowledge of the metamorphosis 

 of the Stomatopoda is still somewhat incomplete, especially with 

 regard to the first stages which hatch from the egg, and the con- 

 nection between the larval forms, that often vary greatly, and the 

 sexual animals to whicli they belong, these last differing less from 

 one another than do the larvae. A general distinction may be made 

 between two types of larvae which, however, are connected together 

 by intermediate types ; these two were formerly classed as separate 

 genera under the names of Erichthus and Alima. Of these two 

 forms the Erichthus shows the more primitive metamorphosis, so 

 that we shall describe this larva first. 



The youngest known stage of the Erichthus series, probably the 

 one at whicli the young animal leaves the egg, is called the 

 Ericlithoidina. The youngest larva known (Fr. Mijllbr and Claus, 

 No. 87) is 2 mm. long, and is seen to be divided into three regions : 

 (1) an anterior, unsegmented cephalic region which carries the eyes, 

 antennae, and mouth-parts, and gives origin to the fold of the dorsal 

 shield which projects backwards; (2) a middle thoracic region hidden 

 under the dorsal shield and consisting of eight segments, the five 

 anterior carrying Copepod-like biramose limbs, while the three 

 posterior segments are limbless; (3) a posterior region in which 



