REPHOUUCTION OF PARTS IN CRUSTACEA. 475 



cavity of the furaiueii is slif,'litly lillud up with a body resem- 

 bling a nucleated cell. This cell is the (^cnn of the future 

 leg, and very shortly increases in size, so as gradually to push 

 out the fdm alluded to above, which is now become a thick 

 strong cicatrix. During the time that this is going on, the 

 whole of the exposed surface had become tense and bulging, 

 but this gradually decreases round the circumference as the 

 central nucleus increases in size, which it does at first longi- 

 tudinally, and then transvereely. As it increases in size, the 

 cicatrix, which still surrounds it as a sac, becomes thinner and 

 thinner, until it bursts, when the limb, which has hitherto 

 been bent upon itself, becomes stretched out, and has all the 

 appearance of a perfect limb, except in size. 



In the lower Crustacea, and even in the lower ^lacronra, 

 we find the power of regeneration more extended ; — a limb 

 broken off at any part of its phalanges will grow. The mode 

 of reproduction in the lobster is peculiar, and differs from the 

 higher Crustacea. Instead of the young limb being folded 

 upon itself, as we found it in the Brachyura, it is quite 

 extended, although apparently enclosed in a sac. 



As far as my observations have yet gone, it appears to me 

 that the germinal cell is derived from one of those which are 

 nearest the central opening on the raw surface. This cell, 

 following the ordinary course of development, by the nucleus 

 breaking up into nucleoli, which in time become parent cells, 

 each of which again undergo the same process. This proceeds 

 for several stages, all the less important cells dissolving and 

 serving as nourishment to the central or more important ones, 

 until the number of centres are reduced to five, the number of 

 joints required, which, by a constant process of a similar nature, 

 assume the form of the future leg. II. I). S. G. 



