379 



Krallenplatte 



Fig, 6 is a section of a claw of a chick taken twelve hours after 

 hatching. No trace of the neonychium remains, it having evidently 

 been rubbed otf by contact with the 

 ground. The points of the claw are 

 now hard and sharp and ready to 

 begin scratching in the ground for 

 food in the characteristic way. 



Fig. 7 is a view of a whole claw, 

 taken from a chick which was in the 

 act of hatching. The neonychium is 

 seen beginning to break away. 



I have found no mention by other 

 authors of anything of the nature of 

 neonychia in birds. 



Neonychium 



Krallensohle 



Fig. 7. Claw of a chick taken 

 in the act of hatching. The neonychium 

 is seen beginning to break away from 

 the rest of the claw. 



III. R e p t i 1 i a. 



The only reptile I have myself 

 examined for neonychia is the large 



lizard Tejus, where they are present in the embryos and are of the 

 chick type. 



Rathke, Voeltzkow and Göldi have all noticed expanded claw 

 tips in the embryos of the crocodilia. This expansion is doubtless due 

 to the presence of neonychia. 



VoELTZKOw's description, dealing with Crocodilus madagascariensis 

 and C. porosus, is much the fullest and he also gives figures of the 

 whole claw, though not of sections. He compares the shape of the 

 embyro claw to the toes of a tree frog or to a mammalian hoof. He 

 states that the expanded portion is either lost shortly before hatching 

 or is worn away afterwards by use. He considers it to be a portion 

 of the Krallensohle, but it is evident from his description and figures 

 that it is the neonychium of other forms. In nearly ripe embryos a 

 thin structureless layer forms dividing the permanent Krallensohle 

 from the portion (neonychium) which is going to be thrown off. He 

 was unable to find corresponding structures in other reptiles, doubtless 

 because the neonychia of other reptiles are of the chick and not of 

 the Crocodilus or Tolypeutes type. 



of it is formed of very loose tissue stained red by treatment with carmine 

 and picric acid which stains the other parts of the claw yellow, while 

 the outer layer is firmer and more fibrous and has a greater affinity 

 for picric acid. In section this outer layer looks to be a direct con- 

 tinuation of the Krallenplatte (Fig. 5). 



