PRIMITIVE PORES OF POLYODOX SPATHULA 461 
corrects some of the erroneous conclusions and figures Collinge 
based upon his poorly preserved material. 
Collinge described and figured the primitive pores as distinct 
sense organs, each having a definite nerve. The material upon 
which his description and accompanying figures were based was 
admittedly poorly preserved, but imagination and a preconcep- 
tion of the structure of a sense organ supplied what the material 
lacked. The only thing in Collinge's figures that corresponds to 
fact is the invagination, and even this is not altogether correct. 
These figures offer an excellent illustration of the danger of 
basing any description and figures of histological structure upon 
poorly preserved material. 
In 1905, during the session of the American Society of Zoolo- 
gists at Ann Arbor, I pointed out Collinge 's errors and gave 
some evidence discrediting the generally accepted view that the 
primitive pores are sense organs. 
In 1906 Kistler- published a paper in which the primitive 
pores are presented as distinct sense organs. The floor of the 
prunitive pore is described and figured as lined by a single layer 
of two types of cell — one a clear supporting cell" and the other 
a darker, club-shaped ''sensor}' cell" with a definite '' slender con- 
ical process" on its free surface and a distinct innervation. 
Fig. 12 is a free copy of Kistler's fig. 6, which illustrates his two 
types of cells. The nerve fibrils have been omitted. 
In 1907 I presented a brief paper on the lateral line system of 
Poh'odon at the VHth International Zoological Congress. In 
this paper I concluded my remarks on the primitive pores with 
the following statement : ' 'The abundance of the peculiar mu- 
cous-like secretion found in many specimens, and the charac- 
ter of the epithelium, indicate at least that the function is not 
primarily that of a special sense organ. If the primitive pore is a 
sense organ at all it is one of low differentiation." The figures 
accompanying the above, while sufficient for general purposes, 
are not correct in the details of the epithelium. The following 
2 The Primitive Pores of Polyodon spathula. By Herbert D. Kistler, B.S. , M.D. 
Jour. Comp. Neur. Psych,, vol. xvi, 1906. 
