No. 407.] DOUBLE LOXOSOM. 895 
it has been possible to determine the number of tentacles they 
have been found unequal on the two lophophores ; one of these 
is therefore in each case more advanced in development than 
the other, as is always the case with two buds which arise side 
by side, the degree of difference being, moreover, such as our 
hypothesis would lead us to expect. 
In the specimen represented in Fig. 5 the brain and the 
stomach correspond in each case to two organs fused. The 
median testis may likewise owe its larger size to its being the 
result of fusion of two testes; but whether that be the case or 
not, its outlet is on the side of the younger individual. The 
mesial budding zone which has been suppressed or remained 
undeveloped is that of the younger individual. The latter fact 
harmonizes well with the theory of fusion, since when two 
buds come into conflict in their development the younger natu- 
rally suffers most. The relations of the median testis, on the 
other hand, can hardly be considered as lending support to 
either hypothesis. 
Fission seems inherently improbable in so highly organized 
an animal as Loxosoma, while against the theory of fusion no 
such objection holds. 
UNIVERSITY OF MINNESOTA, 
July 5, 1900. 
