STRUCTURE AND DEVELOPMENT OF LOXOSOMA. 
325 
rather the tentacular structures developed at the edges of the 
mantle lobes in some of the latter. 
The Rotifera, as has frequently been suggested, in many 
points of their structure resemble the Polyzoa, and more 
especially the Entoprocta: many of these similarities have 
already been indicated by the Hertwigs (31). Salensky (15) 
has drawn attention to the possible homology of the “ antennae ” 
of Rotifers with the posterior sense organs of Loxosoma 
crassicauda. Histologically, the resemblances between Ro- 
tifera and Entoprocta are striking: in the characters of 
their nervous system, muscular fibres, terminations of the 
excretory organs, and so on. Perhaps the similarities between 
the two groups are less striking than those obtaining between 
the Entoprocta and the Trochosphere larvae of Molluscs 
and Chaetopods, but the fact remains that the Rotifera and 
Polyzoa being alike groups which have persisted in the 
Trochosphere stage, must necessarily show a considerable 
number of similarities to one another in various features. 
The affinity between the Polyzoa and the Brachiopoda 
is probably much less close than that between the former and 
the Rotifera and the Trochospheres of Mollusca and 
Chsetopoda, so that the association of the Polyzoa with 
the Brachiopoda as Molluscoidea appears to me un- 
natural, although I do not at all deny the possibility of 
certain affinities between these two groups. It is, further, not 
impossible that Phoronis may (through Actinotrocha) to 
a certain extent connect the Polyzoa with the Brachio- 
poda, although not in the way that Caldwell supposed. 
Summary of Results. 
1. Species investigated : Loxosoma crassicauda, L. pes, 
L. singul are (?), L. Tethyse, and L. Leptoclini, new 
species. The last two alone were studied embryologically. 
2. The adult Loxosoma possesses a large suboesophageal 
ganglion, dumb-bell-like in shape, hitherto described as some 
part of the generative apparatus. The ganglion is developed 
