210 LIFE BY THE SEASHORE. 



closely (Fig. 60). Like them they have an anterior region, 

 not obviously segmented and covered by a shield; a tail 

 region divided into segments and ending in a powerful 

 tail fin, and long feelers colourless in the living animal, 

 and bearing a large scale or squame at their bases. They 

 differ from shrimps, however, in that they seem to have 

 far more legs, and in that many of them have a pouch 

 attached to the posterior legs, as is shown in the ac- 

 companying figure. These are the females, and when 

 adult the pouch will be found to contain developing eggs. 

 The eggs are placed in the pouch when laid, and are 

 carried about by the mother. The members of the order 

 to which Mysis belongs are all very good swimmers, well 

 adapted for life out in the open sea, but, as happens with 

 so many marine animals, the females come inshore at the 

 breeding season. This is partly, no doubt, for the sake 

 of the young when hatched, but probably, in other cases, 

 because the weight of the eggs or young must greatly 

 diminish the swimming power of the mother. Your speci- 

 mens are almost certain to be all females, and a very brief 

 experience will be sufficient to teach you that the large 

 mature specimens are so sensitive to unfavourable condi- 

 tions, that they will not readily live in confinement. In a 

 very short time they lose their lovely tints, become dull and 

 opaque, and drop to the bottom of the jar. You will find 

 that this delicacy of egg-carrying females is common in the 

 Crustacea, and it is profoundly interesting, for it shows how 

 great must be the advantage of the habit of carrying about 

 the eggs, if it can persist against such heavy odds. There 

 are, indeed, few subjects more interesting than the reproduc- 

 tive phenomena of shore animals. 



Before proceeding to the examination of your dead 

 specimens, you should examine the living ones under a 

 lens in a watch-glass filled with sea-water. Whatever be 

 the prevailing tint, and it varies much, you will find the 

 dorsal surface covered with the same beautiful branched 

 pigment cells seen in the shrimp. They are here black in 

 colour and are often arranged segmentally, one for each 

 segment. This is indicated in the figure. The rest of the 

 body may be green, or brown, or transparent, but the 

 anterior region is almost always delicately suffused with 



