4 F. A. SMITT, 



systematical series, where the developmental differences should be expressed by the 

 systematical divisions. For many of the species, that I could examine in some hund- 

 reds of specimens, it was very easy after such a method to determine their systematical 

 relations; but when the evolution fails, leaving one or more stages unmarked, or when 

 we are obliged to determine the natural relations of a species from a little fragment, 

 we must, of course, trust to inference from analogy. It is, therefore, very probable, 

 that many modifications must be made in my essay on the classification and systema- 

 tical distinction of these animals; but it seems to me they should be made in the way, 

 I have proposed for seeking the natural affinities, viz. regarding the individual structure 

 and, particularly, the zooecium, with its changes according to the colonial development, 

 as the only ground for founding systematical divisions. 



Following the order from the lowest to the higher Bryozoa, as I have proposed 

 in my former papers, I should begin with the 



CTENOSTOMATA, 



of which Pourtales' dredgings had brought up a Serialaria. But it was sent me in a 

 bad and dried state, and as I will not venture to give a denomination to such a flex- 

 ible species without seeing the animals; I will only mention it here. 



From this group the zoological as well as the morphological characteristics show 

 two ways of serial evolution. Nearest the Ctenostomata point to the order of 



CYCLOSTOMATA, 



which is represented in this collection by a greater richness of forms and specimens. 

 The family of 



crisie^e 



is here represented by the cosmopolitan 



Crisia eburnea (Pl. I, tigs. 1 — 5) 



in its highest state of evolution, namely, that form denominated C. denticulata. It is here 

 •aptured in two varieties: the one (tigs. 1 — 4) with more slender branches and with the top 

 of the zo(ecia on a level with the foreside of the stern, or only a little raised to free 

 tubes, vertically, from this level. Such is the form that I have represented in three 

 parts of one stem, tigs. 1 — 3, the one tigure to be continued by the other, as the letters 

 indicate *). In the highest parts, as usual, we see the branches grow broader and the 

 zooecia become more uniformly incurved at their tip, vertically, against the level of the 

 foreside of the stem. This form thus approaches the other (lig. 5) more and more, at- 

 taining from the beginning the more typical constitution of the Crisia denticulata. The 

 rigured colony exhibits the zooecia more prolonged in their incurved tips; but with all 

 the variations of this kind, which are sometimes to be found on the same stem, it can- 



') This form, especially in its lower parts, corresponds with the Crisia attenuata, Heller-. Die Bryozoen des 

 Adriatischen Meeres, Wien 1867, pag. 41 (Verh. des K. K. Zool. bot. Gesellsch. in Wien XVII, Bd. 1867, 

 pag. 117). 



