326 THE CRUSTACEA 



last thoracic somites of the female lies a glandular mass, sending 

 numerous fine ducts to the exterior. This is in all probability to 

 be regarded as a cement-gland. 



The eggs are of very small size, and are agglutinated together 

 into a cake-like mass which either lies free in the burrow inhabited 

 by the female or is carried by means of the last three pairs of 

 chelate feet. 



DEVELOPMENT. 



Little is known of the embryonic development of the Stomato- 

 poda, but their later history is extremely remarkable, on account 

 of the prolonged larval life, the complicated metamorphosis, and 

 the fact that the larval forms of the various species differ from each 

 other more widely than do the adults. The later stages, which 

 may reach a great size, form a conspicuous element of the pelagic 

 fauna in the warmer seas, and many species were described by the 

 older observers as adult animals under several generic names. It 

 is very probable, as Hansen points out, that several forms of larvae 

 belong to species and even genera which in their adult state are 

 still to be discovered. 



Two main types of larvae can be distinguished, corresponding 

 to the old genera Eriehthus, Latreille, and Alima, Leach, and the 

 former can be further subdivided into a number of larval genera, 

 Gonerichthus, Lysioerichthus, etc. 



Though the earlier stages of all these are still very imperfectly 

 known, it is certain that great differences exist between them as 

 to the degree of development at the time of hatching. The 

 longest series of larval stages appears to be passed through by 

 certain Erichthus-iorms, especially by those to which the names 

 Lysioerichthus and Coroniderichthvs have been given (larvae of Lysio- 

 squilla and Coronida). In the youngest known stage of this series 

 (Fig. 191, A) three regions of the body can be distinguished: (1) 

 An unsegmented cephalic region bearing the median and paired 

 eyes, antennules, antennae, mandibles, maxillulae, and maxillae, 

 and giving rise to the great carapace which envelops the greater part 

 of the body; (2) a thoracic region of eight somites, all of which are 

 free from the carapace, the first five bearing biramous swimming- 

 feet, while the last three are without appendages ; (3) a broad tail- 

 plate representing the still unsegmented abdomen. In the following 

 stages the abdominal somites are successively segmented off in front 

 of the tail-plate, which remains as the telson, and tlieir appendages 

 at the same time develop in regular order from before backwards, 

 the uropods at first not differing from the appendages in front of 

 them and not preceding them in order of development. The first 

 and second thoracic limbs early lose their exopodites, and the 

 second pair become greatly enlarged and assume their characteristic 



