380 Proceedings of the Royal Physical Society. 



place, and the pincer joints of the new limbs measured — 

 right 2 j^ inches, left 2yV inches. 



It thus appears that in a case where the two chelae are 

 lost at different times, and with a considerable interval be- 

 tween, the two new limbs will be reproduced together at the 

 next ecdysis, if a sufficient time intervenes for the develop- 

 ment of their respective rudiments. 



Eeproduction of Ambulatory Limbs. 



My observations on the reproduction of ambulatory limbs 

 in the lobster are not in accordance with those of Chantran 

 for Astacus. This author maintains that in Astacus the 

 ambulatory limbs, like the chelae, do not attain their full 

 development until the third or fourth ecdysis after their 

 reproduction. Lobster B. supplies evidence on this point. 

 A reference to the record of observations will show that 

 after the ecdysis, 19, v. 83, the rudimentary ambulatory limbs 

 became of the same size as their older fellows, while the 

 chelae required two or three other ecdyses to bring them up 

 to their normal size. This evidence appears to show that in 

 the lobster, at any rate, the new ambulatory limbs attain 

 their full development at the first ecdysis. Indeed, one 

 might be led to expect this from a study of the functions of 

 the different limbs. An ambulatory limb, unless as long as 

 its fellows on the same side, would be of no use for locomo- 

 tion, and so might just as well remain a mere rudiment until 

 such time as it could be reproduced of full size. On the 

 other hand, a pincer claw, although small, is still capable of 

 being used in defence or for seizing prey, and becomes more 

 and more so with each ecdysis. 



Eeproduction of the Antenna. 



The long flagellum of the lobster's antenna is very fragile, 

 and on account of its delicacy often becomes injured during 

 ecdysis. Its reproduction from a rudiment, which is at first 

 conical, and afterwards becomes spirally twisted at the apex, 

 has already been described. The measurements given for 

 specimens B. and C. will show that in the lobster the new 

 flagella do not attain their full development at the first 



