370 Proceedings of the Royal Physical Society. 



XXIX. Notes on the Reproduction of Lost Parts in the Lobster 

 (Homarus vulgaris). By George Brook, Esq., F.L.S., 

 Lecturer on Comparative Embryology in the University 

 of Edinburgh. [Plate XVII.] 



(Read 17tli March 1886.) 



Over a century and a half ago, Eeaumur (1 and 2) pub- 

 lished an elaborate account of the process of ecdysis in 

 Crustacea, and of the manner in which lost or injured limbs 

 are replaced by new ones. His investigations on the repro- 

 duction of lost parts were so complete, that little has been 

 added to them up to the present time. It was lieaumur who 

 first discovered that in the Decapods the injured limbs are 

 usually reproduced from the basal joint. He showed that if 

 a pincer claw is broken at the first, second, or third joint, 

 the mutilated limb is generally cast off at the fourth joint 

 within a few days, and the new limb develops from this 

 point. He adds, however : " Quoiqu'il en soit de la raison 

 pour laquelle les jambes se trouvent communement cassees 

 dans la suture qui est proche de la quatrieme articulation, 

 j'ai vu diverses fois naitre des parties de jambes qui n'avoient 

 qu'une, deux ou trois articulations ; mais elles renaissoient 

 beaucoup plus lentement que celles qui etoient cassees a la 

 suture voisine de la quatrieme jointure." 



His account of the process in Astcccus is shortly as follows : 

 One or two days after a limb has been lost, a reddish mem- 

 brane covers the scar at the end of the remaining joint. In 

 four or five days a small spherical knob makes its appearance 

 in the centre of the membrane, which later becomes conical. 

 The cone gradually increases in size, until at the end of a 

 month or five weeks it is slightly curved towards the head of 

 the animal, and measures six or seven lines in length. As 

 the membrane covering this new growth becomes thinner 

 and thinner, one can see that the new limb is not simple, 

 but jointed. If a pincer claw, a longitudinal furrow marks 

 the division between the two parts of the terminal segment. 



