310 



muscles of the caudal extremity, by which this phenomonon 

 is produced. (See Proceedings, Vol, IV., p. 216.) 



A short lime since one of these animals, an Ophisaurus ventra- 

 lis, was presented to me, in which the lost part was in process 

 of reproduction. I seized upon the opportunity to make a some- 

 what careful microscopical examination of the parts to learn their 

 histological character. 



Some two months before, the animal had lost its tail, and 

 already it had been reproduced to the length of three inches, and 

 was still rapidly growing. Externally the line of junction of the 

 old and new parts was pretty distinct, and the scales on the first 

 inch of the new part were arranged irregularly ; but on the last 

 two inches they were in distinct rows corresponding to those of 

 the old part, so that when the process had been completed the 

 rows of the old and new parts would be continuous throughout. 

 I mention this fact, for it would appear that the scales required 

 some time to arrange themselves conformably to the character- 

 istics of the animal. I divided the animal a short distance above 

 the junction of the old and new parts, and then carefully dissected 

 down to the seat of the reproductive process. The last half inch 

 of the old part presented a highly vascular, injected aspect, not 

 unlike that of the ends of a fractured bone undergoing reparation. 



The process evidently takes place, vertebra after vertebra, 

 together with its muscular and nervous parts, according to "the 

 law of analogous formation." From the osseous, the muscular, 

 and the nervous tissues of the last vertebra of the old part, are 

 thrown out as many kinds of formative plasma, in which are 

 developed, respectively, the new bone, muscle, and nerve. As 

 fast as they are formed they are pushed along successively by 

 new ones which follow behind. The last vertebra, with its 

 appendages, is, therefore, the fruitful parent of all those newly 

 formed, which may be even ten or twelve in number. Upon 

 examining the first vertebra of the new part, and then in pro- 

 cess of formation, I found the development to take place as in 

 embryology, the different tissues going through the usual cell- 

 stages of growth. But the formation of one vertebra is far from 

 being completed before it is succeeded by another, and on this 

 account the first two or three of the new parts appear imperfect, 

 but subsequently become fully formed and joined together. I 

 was particular to examine the spinal cord of the new part, for 



