In a preliminary note' Ostroumoff makes some remarks on the calcareous 

 skeleton in the liriiozoa and comes to a totally dillerent result from N'itsche with 

 regard to its formation. He has hecn able to siiow, namely, by lueans of silver 

 impregnation, that the covering membrane of the zoocia has a distiiiclly cellular 

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

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

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

 I'interieur de cellules ectodermlques«). At another place he stales:- »Le squeletle 

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

 exisle pendant toute la vie de I'animal on comme couche sous-squeletaire 

 (MenibraiiijioraJ ou comme deux couches enlre lesquelles se trouve le s([uelette 

 (LepraliaJ'. 



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

 bastopol, the writer expresses his oj)inion 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 Memhraniporidue, 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 PalUisiana is the only representative 

 of the sj)ccies of 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 its 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. I'ergens 

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

 nary paper: ^ (»bei alien Arten, welche ich untersuchte, war von aus.sen immer die 

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

 ning fossil Brijozoa'', where he says: »Le derme est essentiellement constilue 

 par un nombre variable de cellules aplalies a contour irregulier^ (Ostroumoff). 

 Mes observations sur les larves (jui viennent de se fixer m'ont demontre cpie 

 c'est dans I'interieur de ces cellules cjue se fait le dej)6t de calcaire . In contrast 



' K8, p. 291; ' 89, p. 577; " 90, pp. .J8, J9 ; * 92, p. .'iOG; ' 93, p. :t08. 



