PARASITISM AMONG MISSOURI NAIADES 519 
in.becillis3). However, reference should be made to the author's 
descriptive and illustrated catalogue of Mussourt Naiades‘ for 
detailed accounts of Mussels as parasites as well as that of the 
juvenile and adult life. In this present report the writer would 
employ the same revised nomenclature as used in his general 
catalogue. This revision is made necessary because of the recent 
revival of Rafinesque’s Priority’ and also because of the well deter- 
mined fact that the nutritive and reproductive structures of the 
soft parts serve as far more satisfactory bases for classification than 
shell characters. However, for the sake of clearness, synonyms 
for the revised names appear in the parentheses, as indicated in 
the case of Lastena ohiensis mentioned above. 
Since it has been observed that the nucleus of the pearl, 
found in the Fresh-water Mussel, is that of the remains of some 
mite or worm it is concluded that these parasites so irritate the 
glandular mantle that an abnormal pearly excretion is laid over 
the irritant in regular, but usually, irregular, layers while these 
pearl glands endeavor to functionate normally in building the 
inner, or pearly, lining of the shell. Hence, the writer, while 
engaged in securing data for cataloguing the Nazades of Missouri, 
devoted much incidental attention to the study of Mussel 
perasites since the Pearl Mussel Investigation occupied the 
author’s attention for most of the four years, (1911-1915), when 
ithe greater part of the State came under his actual personal 
survey. As it was his pleasure and profit to make studies of the 
Naiades at the U. S. Fisheries Biological Station, Fairport, Iowa, 
where both natural and artificial production of the fresh-water 
pearl is experimentally studied, some data have been secured 
under the auspices of this Station. For the identification of the 
following tabulated list the writer is indebted to Prof. H. Walton 
Clark, one of the personel of the Fairport Station and a recog- 
nized authority on the natural production of the pearl. 
In order that the delicate soft parts of these parasites, such as 
antenna, thoracic appendages, etc., may be preserved and kept 
pliable for future study Keenike’s Fluid is used, the receipt of 
which is submitted here :— 
7A. DY Howard, science ,N. S:, XU, pp.)353-355, Sept. 4, ror. 
4 American Midland Naturalist, IV, No’s. 3-10, 1915-1916. 
5 |. S. Frierson, Nautilus, XXVIII, pp. 6-8; also E. G. Vanatta, Acad. 
Nat. Sci. Phil., pp. 549-559, Dec. 8, 1915. 
