Chap. XXVII. 



OF PANGENESIS. 



391 



true 



so far as its development depends on the union of the proper 

 gemmules with certain nascent cells, together with the super- 

 abundance of the gemmules derived from both parents and self- 

 multiplied, throws light on a widely different group of facts, 

 which on any ordinary view of development appears very strange. 

 I allude to organs which are abnormally multiplied or transposed. 

 Thus gold-fish often have supernumerary fins placed on various 

 parts of their bodies. We have seen that, when the tail of a 

 lizard is broken off, a double tail is sometimes reproduced, and 

 when the foot of the salamander is divided longitudinally, ad- 

 ditional digits are occasionally formed. When frogs, toads, &c, 

 are born with their limbs doubled, as sometimes occurs, the 

 doubling, as Gervais remarks, 44 cannot be due to the com- 

 plete fusion of two embryos, with the exception of the limbs, 

 for the larvae are limbless. The same argument is applicable 45 

 to certain insects produced with multiple legs or antennas, for 

 these are metamorphosed from apodal or antennaaless larva?. 

 Alphonse Milne-Edwards 46 has described the curious case of 

 a crustacean in which one eye-peduncle supported, instead of a 

 complete eye, only an imperfect cornea, out of the centre of 

 which a portion of an antenna was developed. A case has been 

 recorded 47 of a man who had during both dentitions a double 

 tooth in place of the left second incisor, and he inherited 

 this peculiarity from his paternal grandfather. Several cases 

 are known 48 of additional teeth having been developed in 

 the palate, more especially with horses, and in the orbit of the 

 eye. Certain breeds of sheep bear a whole crowd of horns 

 on their foreheads. Hairs occasionally appear in strange 

 situations, as within the ears of the Siamese hairy family . 

 and hairs " quite natural in structure " have been observed 

 "within the substance of the brain." 49 As many as five spurs 

 have been seen on both legs in certain Game-fowls. In the 

 Polish fowl the male is ornamented with a topknot of hackles 



44 ' Compte Rendu,' Nov. 14 1864 r> 

 800. ' ' F ' 



45 As previously remarked by 

 Quatrefages, in his < Metamorphoses 

 de l'Homme,' &c, 1862, p. 129. 



46 Gunther's 'Zoological Record' 

 1864, p. 279. 



47 Sedgwick, in ' Medico-Chirurg. 

 Review,' April 1863, p. 454. 



48 Isid. Geoffroy St. Hiluire, 'Hist. 

 des Anomalies,' torn, i., 1832, pp. 435, 

 657 ; and torn. ii. p. 560. 



49 Virchow, ' Cellular Pathology,' 

 I860, p. 06. 



