FLORIDAN BRYOZOA. 15 



Zooecia cellularina, fornicata, fere gequilata, reeta, aream aperturae ovalem 0,2 m.m. 

 circ. longam, setas area? marginales 6 — 4 praebent, e quibus par proximale (seta? dua? 

 oppositae, fornici proximse) bifurcatura est. Fornix reniformis in formam cervicornem 

 excavatus, superne saepissime abscissus, marginem internuni, supra et infra pedunculum, 

 in dentem saapissime productnm prsebet. Margo externns avicularii lateralis externi 

 rectam fere lineam cnin latere zooecii deorsnin facit. Vibracnlarinm ad basin zooecii 

 sulcatum, sacciforine, supra dorsum coloniae explanatum, diinidiam fere longitudinem 

 zooecii tenet, parte inferiori partem dorsi superiorem zooecii praecedentis tegit, cujus 

 avicularium 'laterale tangit. Avicularia mediana frontem fere omnium zoo3ciorum mu- 

 niunt. Ooecia parietem poribus pertusum praebent. 



Thus it is very easy to distinguish even this form from the other; but besides 

 the above-named differences, there is one that gives it a totally difterent aspect, viz. 

 the shortness of the zooecia, that makes the apertural area to occupy the greatest part 

 of the front side (see fig. 39). In connexion with this shortness follows the greater 

 and more uniform thickness of the stem and its branches, and with this again we find 

 connected a mode of articulation, which on the arctic Cellularia duplex {Menipea Smittii, 

 Norm.) I have described 1 ). Sometimes in the dichotomisations we find no articula- 

 tion, the branches continually going över into each other through the unbroken zooe- 

 cia (see fig. 40); in other dichotomisations we tind the common articulations (see fig. 

 41) but higher up than usually, so that the median zooecion, on each side of it, carries 

 an unbroken younger zooecion, instead of being itself the youngest unbroken zooecion 

 in the internode. 



The Cellularia cervicorjiis, in the collections of Floridan Bryozoa by Pourtales, 

 seems to be more common than the other forms of this genus. It is taken by him 

 from the depths of 7, 9 and 17 fathoms. 



Now if we try to consider the relations that exist between these three Floridan 

 CellularioB, they very closely agree just in the point noted by Busk as the most cha- 

 racteristical for his Cellularia cervicornis, viz. the peculiar markings on the fornix. Fur- 

 thermore the distinctive characteristics are connected with each other, from C. pusilla 

 to C. cervicornis, through the intermediate C. cornigera, that I have placed between 

 them. Thus wc lind the greater developraent of the vibracularium and the diminishing 

 proportions of the lateral avicularium following each other in such a series, at the 

 same tirne as the median avicularium becomes more constant, these organs, as usually in 

 this group, compensating each other, so that the greater development of the one takes 

 with it a diminution of the other. In this respect the three forms would be arranged 

 after the same principles that are followed by the whole genus Cellularia in its diver- 

 gence towards the Caberean type; but other circumstances seem to show that they do 

 not belong to the same or at least to an unbroken evolutional series. Thus the denti- 

 culation of the radical tubes (soboles) of the C. cornigera, and the bifurcation of the 

 two proximal marginal bristles (spines, Busk) of the C. cervicornis, can-not be account- 

 ed for by any known evolutional law for this genus. With a greater store of speci- 



! ) Krit. Fört, Öfvers. Vet.-Akad. Förh. 1867, p. 312. 



