Ill a preliminary note> Ostroumoff makes some remarks on the calcareous 

 skeleton in the Brgozoa and comes to a totally different result from Nitsche with 

 regard to its formation. He has been able to show, namely, by means of silver 

 impregnation, that the covering membrane of the zooecia has a distinctly cellular 

 structure, over which he found a thin cuticle and under it the calcareous 

 skeleton. He concludes from this that the chalk particles are deposited within 

 the ectoderm cells (»par consequence les particles calcaires se deposent dans 

 I'interieur de cellules ectodermiques^)- At another place he states:^ »Le squelette 

 calcaire de nos Bryozoaires se place parmi les cellules de I'exoderme. Le dernier 

 existe pendant toute la vie de I'animal ou comme couche sous-squeletaire 

 (MembraniporaJ ou comme deux couches entre lesquelles se trouve le squelette 

 (LepraliaJ " . 



Later in the main work' which deals with the Bryozoa from the Bay of Se- 

 bastopol, the writer expresses his opinion about the same subject in this way: 

 »in the family Escharidae (such as for instance in Lepralia) the calcareous 

 skeleton during its formation divides the ectoderm into two layers, an exterior 

 lying over the skeleton, and which is readily seen on the opercular wall on 

 living individuals as well as on those treated with silver nitrate, and an 

 interior under the skeleton which can only be seen by means of silver impreg- 

 nation. There is only one layer of cells in Membraniporidae, and this is only 

 found below the skeleton «. 



Ostroumoff's observations are based on the small number of species which 

 are found in the Gulf of Sebastopol, and Lepralia Pallasiana is the only representative 

 of the species oi Escharidae which he has been able to examine; it belongs to the 

 forms which develop a calcareous layer, the Cryptocyst, under the covering 

 membrane of the frontal surface, but separated from this by an intermediate space, 

 and having a cellular lining on both it^ surfaces. This is however not an absolute 

 proof that calcification has taken place within the cells, so that Ostroumoff 

 has just as little as Nitsche proved the correctness of his view. Per gens 

 expresses a view similar to that of the Russian writer, partly in a small pi-elimi- 

 narj' paper:* (»bei alien Arten, welche ich untersuchte, war von aussen immer die 

 Cuticula und der Kalk innerhalb der Zelle gelagert«), partly in a paper concer- 

 ning fossil Bryozoa^, where he says: »Le derme est essentiellement constitue 

 par un nombre variable de cellules aplaties a contour irreguliers (Ostroumoff). 

 Mes observations sur les larves qui viennent de se fixer m'ont demontre que 

 c'est dans I'interieur de ces cellules que se fait le depot de calcaire*. In contrast 



' 88, p. 291; ' 89, p. 577; » 90, pp. 58, 59; * 92, p. 506; ' 93, p. 308. 



