LitcTtxry Notices. v 



have assumed that these ampuUary organs are differentiated parts of 

 the lateral line system of sense organs, and many have compared them 

 with the lines of pit organs of ganoids and teleosts. These pit lines 

 are variously developed in different species of fishes, but are always 

 arranged according to a tolerably definite and uniform pattern, and it 

 would appear that they may in some cases be represented topographi- 

 cally by true lateral line canals and that in other cases the typical canals 

 may be represented by similar rows of naked pit organs. These lines 

 of pit organs therefore undoubtedly represent imperfectly developed 

 lateral line canals. 



Now, Mr. Allis calls attention to certain lines of organs (not am- 

 pullae) in the sharks which, together with some segments of the canal 

 system of these fishes, appear to represent the characteristic lines of 

 pit organs in ganoids and teleosts. He therefore concludes that the 

 ampullary organs of elasmobranchs cannot represent the pit organs of 

 higher fishes since these are otherwise provided for. This conclusion 

 is reenforced by the important observation that in the younger embryos 

 examined the ampuUary organs arise scattered over the whole surface 

 of the skin at the positions of the pores of the ampullae, not in the posi- 

 tions of the clustered sensory ends of these tubes in the adult. I quote 

 a part of his description : "The ampullae in my 55 mm. embryo were 

 nearly all represented by small teat-like processes that arose from the 

 inner surface of the ectoderm, and projected into the underlying tis- 

 sues. Some of these processes seemed solid, while others contained 

 a small central lumen which sometimes led to the outer surface, the 

 process then appearing as a sharp fold of the entire ectoderm. A small 

 nerve was easily traced to the inner end of each process. While no 

 attempt was made to trace the complete and definite distribution of 

 these little processes, it was easily to be seen that in certain places they 

 had exactly the relations to the lateral canals that the surface pores of 

 the ampullary tubes have in the 12.2 cm. embryo. This seemed to me 

 to indicate that it must be the pore in the adult, and not the ampulla, 

 that indicates the place of origin of the structure. Here, then, from 

 the primary distribution of these organs, as indicated by their surface 

 pores, was perhaps a manner of determining whether they arose from 

 pit organs or from terminal buds. . . . The long ampullary tube 

 that is found in the latter embryo must then be formed by an exceed- 

 ingly rapid growth of the short process of the younger one, that proc- 

 ess being, so to speak, stretched out into a long tube between the fixed 

 point represented by its surface opening and another relatively fixed 

 one, represented by the point where the sensory nerve enters the 



