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individuals of two species, I cannot tell either whether slight 
differences I observe in their eggs are specific characters or not. If 
I so desire, I may assert that there are two species ; but, in that case, 
others will certainly demand proofs of such a statement. Dr. Sambon 
pretends that the two shapes of the egg found in association with 
Sch. hmnatobiuvi belong to two different species, but I cannot see 
that he can possibly prove this zoologically without finding distinc¬ 
tive differences between the adults. For the proof must consist in 
showing that one form of egg is constantly connected with a certain 
anatomical structure, and the other form as constantly connected with 
another anatomical structure of the adults. Until this is done I am 
afraid that Sch. mansoni will find little approval with zoologists, 
in spite of Dr. Sambon’s contention that ‘ to zoologists the characters 
of the ovum should suffice for the determination of a new species 
(1908a, p. 31). 
The remarkable difference in the position of the spine of the egg 
of Sch. hceniatobuDH has long attracted the attention of observers, the 
majority of whom considered the egg with the end spine as the 
normal, and that with the side spine as abnormal. Various attempts 
have been made to explain the formation of the latter. Dr. SAMBON 
refers to these theories, but in a rather peculiar manner. He parti¬ 
cularly mentions Fritsch, ' who had described certain differences in 
the genital tract of the female, but was under the impression that the 
females containing the lateral-spined ova belonged to the same 
species as those containing terminal-spined ova. He therefore 
explained the difference by abnormality. FriTSCH's explanation was 
obviously wrong, but his description was perfectly correct’ (1908b, p. 
46)- I should like to know in what way Dr. SAMBON has obtained 
the evidence for the concluding part of this statement. He has said 
that the two females he had an opportunity of examining were so 
badly preserved that any study of their anatomy was precluded. 
How, then, does Dr. SAMBON know that FriTSCH's description was 
‘ perfectly correct ’ ? I doubt whether he has at all read that author s 
original article (it is, unfortunately, not accessible to me at present); 
he has certainly not read the later descriptions of LORTET and 
VlALLETON, Leuckart and myself, in the latter two of which 
FriTSCH’s statements with regard to the point under discussion are 
refuted as incorrect. 
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