26 



rosette-plates. While Nitsche' in his above-mentioned work on Membr. mem- 

 branacea has rightly observed, that the single zocecia have independent lateral 

 walls, he gives a wrong view of the relation of the single zocEcia to the rosette- 

 plates. He says namely: »Die Rosettenplatten eines jeden Zoocium correspon- 

 diren nun mit den Rosettenplatten der umliegenden Zoocien auf das genauestes 

 and he gives in detail an explicit account of how the rosette-plates of each 

 zooecium are placed opposite to a corresponding rosette-plate in an adjoining 

 zooecium. If for instance we separate a row of zooecia of a Scrupocellaria form 

 (PI. II, figs. 7 g, 8 c) each lateral wall in its distal half will show a multiporous 

 rosette-plate, but in its proximal half an opening of the same shape and 

 size. If we subject Flastra foliacea (PI. I, fig. 8 b) to the same treatment, we find 

 2(— 3) multiporous rosette-plates on its distal half, and 2(— 3) openings on its 

 proximal half. Because of the arrangement of the zooecia in alternating longitudinal 

 rows, one or more openings in the proximal half of a lateral wall will always 

 correspond to and fit exactly opposite the same number of rosette-plates in the 

 distal half of the corresponding lateral wall of the adjoining zocecium. In Ge- 

 mellaria loricata we have an example of a form, the zocecia of which in contrast 

 to the ordinary conditions are arranged in pairs. Each two of these zocecia are 

 as a rule connected by a single rosette-plate, which only belongs to the one 

 zooecium, while the opposite one has a corresponding opening in the wall. We 

 may examine ever so many forms in this regard, but we will never find two 

 rosette-plates opposite each other, but a rosette-plate on one wall always corre- 

 sponds with an opening on the opposite wall. Strictly speaking the rosette-plate, 

 as well as the apparently single lateral wall between two adjoining zooecia, is 

 also divided into two halves (PI. XVII, fig. 10 b), which however in the case of 

 the rosette-plate are very unequal in size, as the concave pore-bearing portion 

 belongs to Ihe one wall, while the opjjbsite wall includes the pore-ring, which 

 can then be seen on the inner (towards the inside of the corresponding zooecium) 

 surface of this wall as a more or less circular projection round the above-men- 

 tioned opening. The rosette-plates are arched inwardly towards the proximal 

 zooecium on the terminal partition-wall, which as already said is common to 

 two zooecia situated behind each other. The above-discussed arrangement of the 

 rosette-plates can be illustrated in a very clear way by means of a variety of 

 Flastra seciirifrons^ with narrow branches found in the Kara Sea, in which the 

 rather numerous uniporous rosette-plates are unusually strongly arched, so that 

 they can be seen through the membranous oral wall. Inwardly arched rosette- 



' 79, p. 42; ' 53, PI. XXVI, fig. 9. 



