118 
TOPULAR SCIENCE REVIEW. 
associated the function of a rudimentary heart or respiratory 
organ, and in this particular group they are most generally 
situated at the posterior extremity of the monad’s body. 
Passing now from such characters as are shared in common 
by all the members of the Flagellate group to those which serve 
to distinguish them individually from each other, one is amazed at 
the infinity of form and variation in the arrangement of similar 
primary elements that are presented. The essentially plant-like 
aspect of many of these constitutes one of their most conspicuous 
features, to which has also to be added the remarkable extent 
to which will be here found foreshadowed on a much more 
minute but surpassingly luxuriant scale those individual or 
aggregated types of growth hitherto supposed to be confined 
to the more highly organized Ciliate order of the Infusoria. 
Examined from this latter point of view, the various species of 
Codosiga , consisting of numerous individual monads grouped 
together on a simple or branching footstalk, immediately recall 
to mind the compound pelicellate colonies of Ejpistylis or Zoo- 
thamnium ; few, however, among these latter presenting such an 
exuberance and symmetry of growth as is instanced by the forms 
Codosiga cymosa , alloides , and umbellata , illustrated by figs. 
1 , 4, and 5, on the first of the accompanying plates (PI. III.). 
The solitary species, belonging to the genus Monosiga , again, 
ib. figs. 1 6 and 1 8, may be accepted as corresponding with the 
simple and initial factor of the group typified in the same higher 
Ciliate order by the genus Vorticella. This simile in association 
with the family of the Vorticellidse may be carried yet further, 
for while among these latter there occur genera, e.g ., Cothurnia 
and Vaginicola, in which the animalcules secrete around them 
chitinous protective sheaths or loricse, so likewise we find what 
may be regarded as an homologous structure repeated in the 
genus Salpingceca (Plate TV. figs. 2, 9, 11, &c.), though in this 
instance with a diversity of contour altogether unapproached in 
either of those higher types. This genus Salpingceca is alone, 
in fact, worthy of independent study if only on account of the 
exquisite variety of form presented by these protective sheaths, 
many of which may be said to vie in chasteness and elegance 
of design with, the classic vases and amphorae of the ancient 
Greeks. In the genus Lagenceca (Plate IV. fig. 42) is found 
a freely floating loricate type, which may be compared with the 
Ciliate genera Tintinnus or Codonella; while in Polynoeca 
(Plate IV. fig. 1) is encountered a variety whose compound 
lorica resembles the polypary of a minute Sertularian Zoophyte, 
and which has no parallel among that higher order of the 
Protozoa with which previous comparisons have been instituted. 
Not less interesting than the varied forms of the protective 
loricse of these collar-bearing monads as above referred to, are 
