146 
April20, 1906. Twelve small and medium sized specimens. 
April 16, 1907. Ten small and medium sized specimens. 
November 27, 1907. Nine specimens, mostly small and 
medium sized, but one large, with forty-one arms 100 mm. long; 
this last has the IIBr and IIIBr series 4 (3 + 4), the single 
IV Br series 2. 
January 9, 1908. Twelve specimens. 
A critical examination of a large series of specimens at hand 
from the Philippine Islands, taken in connection with the material 
under discussion, shows that rotalaria and parvicirra, as under- 
stood by Dr. Carpenter, are in reality the. same. The only 
criterion used in the differentiation of the two is the number of 
the IIBr plates; but in the Philippine series some specimens have 
all IIBr series 2, others all 4 (3 + 4), though the most common 
arrangement is a majority 4 (3 + 4) and a minority 2. It is 
rarely that we find a specimen with all the IIBr series 2; I have 
been able to examine one or two such, though others have been 
recorded by Hartlaub. Even in Carpenter's examples which 
he unhesitatingly refers to rotalaria (as opposed to parvicirra) he 
states that 4 (3 + 4) series were ”"abnormally” present. 
Carpenter was loth to believe that a single species could 
be both ””bi-” and "tri-distichate”; he observed .the more or less 
frequent occurrence of both forms in the same individual, but he 
assigned the specimens to their systematic position on the strength 
of the character of the majority of their series. This is usually 
a safe enough guide, but in a few cases, such as this, it is un- 
reliable, and leads to erroneous conclusions. Minckert, on the 
other hand, had gone too far in the opposite direction; he credits 
a certain Caribbean species. of Charitometrinæ, Crinometra brevi- 
pinna, with the possession of IIBr series which may be all 4 
(3 + 4), all 2, or both in any combination, and he even makes 
it the type of a new "group", the "”Brevipinna group”. In reality 
he has confused a number of perfectly distinct species some of 
which have one arrangement, some the other, none, .however, having 
