bo 
vo 
THE NAUTILUS. 
A reniform Bivalve, Unio margaritifer v. sinuata Lam. 
The parts of the shell and their names are similarly depicted. 
Section through the shell 
of Clausilia laminata 
(Mont.) x 2, showing the 
nearly straight columella. 
Pyriform univalve, Clau- 
silia laminata (Mont.). 
The questions of species and varieties are 
then discussed at length. The definition of 
“species” is good; but that of “ variety” 
seems to us to beg the question entirely. 
Thus, in one paragraph, a variety is said to 
be an incipient species ; in another, “ varie- 
ties may be individual, that is, occurring 
only in a more or less isolated and sporadic 
way, or they may be a sexual character,” 
etc. American naturalists, at least, do not 
regard such deviations as this as “varieties,” 
but use that term for what Mr. Taylor calls 
“a sub-species, geographic variety or race.” 
We believe that sexual and “random” 
variations should have no place in specific 
nomenclature. It is also unfortunate that 
Mr. Taylor (in common with Mme, Paulucci and others) uses the 
term “mutation ” to express a slighter modification than ‘‘ variety,” 
as it has a very different significance in paleontology, expressing 
the successive stages of a specific form, or genetically related series 
of specific forms, in successive formations. 
In treating of the causes of form-modification in shells, Mr. Tay- 
lor states that fluviatile species tend to develop a lengthened shell 
under the influence of a steady and rapid current, and short forms 
of otherwise elongated species in lakes and other large bodies of 
water. 
