184 NATURE AND AFFINITIES OF THE SPONGES. 



Figs. 24 and 25, which represent phases of these reproductive structures, as 

 observed by the author in the common calcareous sponge Grant ia comprcssa. 

 The collars left out and it is admitted that without much care and patience 

 in examination they are, like the collars of the independent collared monads 

 and Spongozoa, most difficult to recognize the structure accords completely 

 with that vesicular, moruloid embryonic type so abundantly figured and 

 described by Oscar Schmidt, F. E. Schulze, and Metschnikofif. Neither of 

 these biologists appear to have detected the existence of that important 

 element, the collar. That such a structure, however, positively exists, does 

 not rest only upon testimony submitted by the present author, it being 

 substantially confirmed by the independent investigation of Barrois, and 

 even Haeckel. The former of these two authorities indicates, though 

 feebly, the possession of collars by the motile reproductive gemmules of 

 Halisarca lobularis, while Professor Haeckel still more clearly denotes their 

 existence in his representations of his so-called ciliated larvae or gastrulae 

 of the calcareous sponges Leuculmis echinus and Sycyssa Huxleyi. With 

 both Haeckel and Barrois, however, the collared cells have apparently no 

 significance beyond that of ordinary ciliated epithelium, the special function 

 of the funnel-shaped collar, and its import with relation to both the sponge- 

 monads and the entire order of independent organisms described in this 

 volume under the title of the Choano-Flagellata, being as yet unrecognized. 

 It is not only in connection with the simpler moruloid type of the 

 ciliated sponge-gemmule that its fundamental composition out of typical 

 collar-bearing zooids is made manifest. A like interpretation applies with 

 equal force to that seemingly more complex amphiblastuloid type upon 

 which an agreement with the Metazoic embryologic formula has been most 

 powerfully upheld. This may be demonstrated in connection with the 

 identical sponge-form, Grantia compressa, cited in the previous instance. 

 As shown at PI. IX. Figs. 26-29, tn ' s amphiblastuloid reproductive body 

 may, furthermore, present three very distinct developmental phases. It may, 

 as in the first instance, Fig. 26, exhibit typical collared cells in the posterior 

 or basal hemisphere, and simply flagellate ones in the anterior one ; in 

 a second case, Fig. 27, the basal elements may be simply amoeboid and 

 the anterior flagellate, this representing indeed the characteristic condition 

 under which the amphiblastuloid type has been most extensively figured 

 and described. A modification of this type, in which the basal amcebiform 

 units project irregularly from the periphery, is shown at Fig. 29. In the 

 third and remaining form, Fig. 28, the basal elements are also amoeboid, 

 but the anterior ones, in place of being simply flagellate, bear also charac- 

 teristic hyaline collars. These three are, in fact, progressional phases only 

 of one and the same fundamental amphiblastuloid type, the latter again 

 being an unevenly developed variation only of the simpler and homogene- 

 ously constructed moruloid form. In the moruloid type, Figs. 22 to 25, the 

 development of the collared units has progressed evenly throughout the 

 entire series, while in the three amphiblastuloid ones above enumerated, it 



