336 Variation in Shells. [ZOE 
Var. cypreaphila Newc. 
Var. ramentosa Gld. 
‘Var. exarata Pfr. 
Var. Nickliniana Lea. 
I have these forms so closely connected with H. arrosa that no 
doubt can exist as to their relations. 
Var. cypreaphila, passes to the eastward and occupies the foothills 
of the Sierra Nevada Mountains, and evolves in turn the darker 
and more wrinkled form known as H. /udicu/ata Binney, which in 
turn sends off numerous varieties into the adjacent mountains, and 
at San Diego completely seals up its umbilicus, while the mountain 
colonies keep their umbilicus open or only partially closed. 
Var. ramentosa, var. exarata and var. Nickliniana, have spread 
over the Coast Range as far south as Monterey Bay, which is 
also the southern limit, so far as we know at present, of the typical 
fT. arrosa. In this small area, however; these forms have sent 
out almost innumerable varieties, and all have become _inter- 
woven like a piece of lace-work. On the south side of Monterey 
Bay an extremely elevated form of var. Wickliniana appears, which 
we know under the name of A. Californiensis; and, unfortunately, 
this form was the first one described of this group, and we are com- 
pelled to observe the unnatural arrangement of grouping the other 
members around it. Var. Nickliniana, does not appear to the south- 
ward again on the mainland, but it has been transplanted in some 
way onto Santa Catalina Island, where it has become thoroughly 
established, though somewhat changed in form and very variable in 
coloring, and is known to conchologists as H. Kelletti, On the 
mainland south of Santa Catalina Island the form again becomes 
slightly modified, and passes under the name of var. Stearnsiana. 
If the shells themselves are a guide or an index to their relations, 
I have this record so complete that but little doubt can exist as to 
its truth. 
In closing, I may add that my impressions: are variation is in- 
herent in matter, the primary cause being chemical action or affi- 
nity. 
The conditions of the environment, such as food, heat, light, 
air and moisture, etc., act as aids or checks to the primary cause. 
_ Perhaps imperfect fertilization of the ovaries, through what we 
call close blood relatives, and. chemical changes IO: the vital 
