NATURE AND AFFINITIES OF THE SPONGES. 191 



remained immersed within, a common gelatinous matrix, or " zoocytium," 

 such as actually exists in the several genera Spongoinonas, Phalanstcriuvi, 

 and Ophrydimn, taking there the place of a dendritic pedicle. \\\ AnthopJiysa 

 vegetans, furthermore, as shown at PI. XVIII. Figs 2, 4, 5, the propagation 

 of the species by the detachment of entire uvclloid masses corresponding 

 essentially with the rosette-like clusters of Halisarca, is well substantiated. 

 A still more pertinent comparison in this direction may, however, be insti- 

 tuted between the rosette-gemmules of Halisarca Dujardinii delineated at 

 PI. IX. Figs. 19 and 20, and the monad aggregate of Codosiga botrytis 

 reproduced from Stein's drawings at PI. IV. Fig. 6. 



Summing up the entire evidence now submitted with reference to the 

 structural and developmental phenomena of the Spongida, and correlatino- 

 it with that embodied in this volume relative to those of the independent 

 Choano-Flagellata and other Flagellate Protozoa, scarcely a shadow of 

 doubt even is admissible concerning the intimate and thoroughgoino- relation- 

 ship that subsists between one and the other. The primary and essential 

 element of the apparently complex sponge-stock is the assemblage of 

 collared flagellate zooids that inhabit its interstitial cavities under various 

 plans of distribution. Individually, these collared zooids correspond, struc- 

 turally and functionally, in every detail with the separate collared units of 

 such genera as Codosiga, Salpingxca, and Protospongia, The collar in either 

 case presents the same structure and functions, exhibits the same circu- 

 latory currents or cyclosis, and acts in a precisely similar manner as a trap 

 for the capture of food. The body contains an identical centrally located 

 spheroidal nucleus or endoplast, and a corresponding, posteriorly located, 

 series of rhythmically pulsating contractile vesicles. The developmental and 

 reproductive phenomena are also strictly parallel. Both originate as simple 

 amoebae or simple flagellate monads exhibiting no trace, in their earliest 

 developmental phase, of the subsequently acquired characteristic collar. 

 Both again, after passing matured age, withdraw their collar and flagellum, 

 and assume an amoeboid state. Then, coalescing or not with their fellows, 

 they enter upon a quiescent or encysted condition, and breaking up into a 

 greater or fewer number of sporular bodies, provide for the further existence 

 and distribution of the species. Among the independent collared types this 

 sporular progeny, except in Protospongia and Phalansterinm, is scattered 

 through the surrounding water, while in the sponge they are retained 

 within the common gelatinous matrix, or cytoblastema, and assist in the 

 extension of the common colony. More exceptionally, for the purpose of 

 securing the local distribution of the species, the coalescing amcebiform 

 zooids of the sponge-stock, derived from the metamorphosed collared 

 zooids, form by repeated segmentation a pseud-embryo, or so-called ciliated 

 larva, of considerable size, whose cell-constituents when analyzed are found 

 to consist of typical collared zooids, resembling those from whence they 

 previously originated, and presenting similarly in their earliest phase of 



