Alexander Agassiz Laboratory 
HOPKINS MARINE STATION 
PACIFIC GROVE 
CALIFORNIA 
Jacques Loeb Laboratory 
July 30, 1940 
Dr. Waldo L. Schmitt, 
U. S. National Museum, 
Washington, D. C. 
Dear Waldo; 
Your letter regarding the photographing of crabs 
^ I M HV 
as a method of measurement has been recieved.On the whole I 
fear that I lack enthusiam and seeH possible difficulies - 
must be getting old and conservative. 
It is certainly an advantage to ^e able to go back 
and take additional measurements if you want to later. It 
would save time in the field and the measurements in the lab 
could largely be done with clerical help. A difficulty that 
might arise would be that of depth of focus. As ordinarily used 
for books it is intended for flat objects and it is possible that 
parts below the glass at any distance would be out of foeue 
unless the lens were stopped down and the exposure lengthened. 
I have also worked in a momber of places where there was no 
electricity. 
As to the accuracy that does not seem a difficulty 
For an animal of that size measurements to the nearest mm. 
would be adequate. I fear that a plate ruled to mm. would 
bbscure the crab below; I should think that: cm. with the mm. 
indicated on the lines rather than a complete grid would be 
enough. Length and breadth are the most important for following 
growth and, as you say, these could be easily determined 
unless the crabs are very "dirty". If you i®an get an Instrument 
you could try it out on a crab of that sort and quickly get 
an idea of the difficulties. 
It is possible that I may be on the campus on the 
week end of the 11th so it would be well to phone down to 
galo Alto from San Francisco as you suggest. If it is Sat. 
afternoon or Sunday the dept, cannot be reached. I may be at 
Palo Alto 6618; if that fails^ try Dr. Victor Hall, P. A. 5240 
or Dr. Jefferson Crismon, P.A. 8182. If I am in town they 
will know it. I have no phone at my residence here; the 
Station number is Monterey 5889. 
^ I M HV 
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