251 
we find for inst. Thwjaria thuja and Thuj. lonchitis referred to' the 
genus Cellaria and placed between Cellaria (Crisia) eburnea and 
Cell. (Bicellariella) ciliata. ; 
While the older Bryozoan systems are based ” entirely on 
diversities in the form of the colony Smitt and Hincks lay the 
chief stress on the form and structure of the zooids, and this view 
must at present be regarded as the dominant. As, however, in 
the Hydroids most authors as systematic. characters still preter 
zoarial diversities to zooidal, I think it might be of use in general 
to examine the question how great systematic importance may be 
ascribed to the form of the colony, and I shall first give some 
quotations from the few authors who have treated this question 
with respect to the Bryozoa. The first quotation is from the late 
Th. Hincks!) who has played a chief part in the working out 
of a more natural Bryozoan system, 'and has, besides, done such 
excellent work also in the Hydroid polyps. After having spoken 
about the slight help, which the polypide, and the avicularia 
give us in systematic regard, he continues: "There remain the 
characters of the cell?) itself and the habit of growth. It can 
hardly be deemed doubtful which of them should have the prece- 
dence in a natural system; we may go very much further, indeed, 
and say that in such a system the latter must hold a very 
secondary and subordinate place. The essential structure of the 
cell”), as one of- the primary zooidal”) forms, must certainly be 
accounted the most important point both in itself and as a clue 
fo relationship. The mere habit is, so to speak, a superinduced 
condition, which may be different in the most nearly related and 
similar in the most divergent forms, and groups based on it, 
1) 28, Introd., p. CXXVIII. 
?”) By the ”cell” is here meant the zooecium. 
1) According to the old eystid theory the zooecium and the nutritive 
apparatus (the polypide) were both regarded as individuals (zo0ids). 
The above citation from Hincks has also been used in my work on 
the cheilostomatous bryozoa (35, p. 68), but by a mistake the word 
"zooidal” has been replaced by ""zooecial”. | 
