ON MYSIS. 17 



a proportional growth in the four lateral members fig. 10. c. 

 and which are the rudiments of the two pair of antennae in 

 the perfect animal , the embryo going on thus with a 

 progressional developement from day to day, begins to 

 assume a more complete form, and 'an approximation to 

 that of the parent, fig. 11, in which stage the divisions of 

 the abdomen, the tail, the pedunculate eyes, and the 

 various members are sufficiently distinct ; a still more 

 close resemblance to the perfect animal is attained before 

 the young are finally excluded, which is effected by the 

 parent spreading open the valves of its pouch, when the 

 whole brood emerge at once into the ambient element, and 

 in most of the species, continue associated with the com- 

 munity from which they sprang : the slight differences 

 which they now present, (and which are necessary to be 

 known in order to preclude the possibility of their being 

 mistaken for individuals of a different species,) affect only 

 the inner rows of feet, the sub-abdominal fins, the outer 

 antennae and the tail ; the first of these, in place of the 

 multi-articulate termination seen in Plate I. fig. 8. a. have 

 but one or two short joints and a curved claw fig. 12, 

 superadded to the end of the tibiae, and hence this division 

 of the limb is shorter in proportion ; the sub-abdominal 

 fins consist only of a linear joint surmounted by a few 

 bristly hairs, and do not put on the elegant appearance 

 seen in fig. 9 ; the outer antennae differ in no other respect 

 than in the ciliated scale which is attached to their base, 

 being shorter and less developed, as is also the brush 

 of hair in the males fig 5 ; the three intermediate scales 

 of the tail are proportionably shorter, but yet present the 

 character peculiar to the species, in their form, indenta- 

 tions, and appendages, so as to testify the acuteness of 

 Dr. Leach in having fixed upon this part to distinguish the 

 species from each other. 



AVliat is further remarkable of the embryo, is the way 

 in which they are arranged within the pouch from the 



