69 



should be based almost wholly on the zocecial character; but I am certainly not 

 prepared to hold that other structural elements should never be taken into ac- 

 count. The Flustridae, which seem to constitute a most natural group, have a 

 true Membraniporidan cell, and hold their separate place by virtue of their 

 corneous and foliaceous zoaria«. As a consequence of the weight the writer 

 attaches to the colonial form in the family Flustridae, he refers an incrusting 

 species Flmtra (Memhranipord) flustroides Hincks, which in its essential characters 

 is a Fliistra, to Membranipora at the same time that he indicates in its specific 

 name its likeness or relationship to other Flustra species. Gemellaria is also a 

 genus, which in Hincks is based essentially on the colonial form. 



A. M. Norman^ takes up a somewhat similar standpoint to that of Hincks, 

 which he expresses as follows: »It has been argued by recent writeis that the 

 form which a colony of a polyzoon belonging to the Cheilostomata assumes is of 

 no moment in generic character. Electra pilosa lends strong support to this 

 view. Yet it is a view nevertheless in which I am not prepared in all eases to 

 acquiesce. The zooecial characters are unquestionably all important, but no lasting 

 classification can be based on any part of the zooecium, whether it be the mouth- 

 opening, wall, rosette-plates or anything else. Why also in all instances is the 

 ultimate growth and form of the zoarium to be excluded from generic character 

 among certain families of the Cheilostomata, and at the same time to be recogni- 

 zed among the Cyclostomata and Ctenostomata, and even other groups of the 

 Cheilostomata? This is surely scarcely consistent. In some instances, as for example 

 in Electra pilosa, the form of the colony is of no generic and specific value, but 

 in other cases it may be and, I believe, is«. To judge from this statement this 

 writer seems more inclined than Hincks to use the colonial form as a syste- 

 matic character, and this appears also in his last paper ^ on the Bryozoa, since 

 he here maintains the old Flustra genus Carbasea rejected by Hincks, which is 

 only based on the fact that the colony has a single layer. There is of course no 

 doubt, that any character constantly appearing in a systematic division must 

 be regarded as being of systematic value, and the same must also be the case 

 with the colonial form. Wherever therefore this appears constantly within a genus 

 or family it ought to be emphasized in the diagnosis. But the proof that the 

 respective genus or family is a natural one is only given when evidence has been 

 obtained of sufficiently great agreement between the single species in regard to 

 the structure of the colonial individuals, since for instance the same form of 

 colony may appear in the Bryozoa not only within the three natural main divi- 



» 82, p. 122. '■' 83, p. 581. 



