l6o NATURE AND AFFINITIES OF THE SPONGES. 



channel selected by him for the introduction to the scientific world of what 

 appeared to be an entirely new and remarkable little group of organisms. 

 Professor Haeckel had previously declared, in his ' Monograph of the 

 Calcispongiae,' his belief that the so-called "gastrula" or "ciliated larva" 

 of a sponge typified the permanent and adult condition of some pre- 

 existing type which might be appropriately designated an arcJiegasUnda, 

 and that probably a very close approach to this hypothetic archetype was 

 furnished by the supposed little sponge-form first described by Dr. Bower- 

 bank under the title of HdlipJiysema Tiunanozviczii. In the ' Biologische 

 Studien ' Haeckel announces, as the results of his most recent personal 

 investigation, the discovery of a series of forms generically identical for 

 the most part with this type ; that his former anticipations were fully 

 verified ; and that in HalipJiysema, and its allies, the true archetype of all 

 sponges and the entire Metazoic series was at length forthcoming. As 

 interpreted by Haeckel, HalipJiysema was declared to be simply an attached 

 sac-like "gastrula," having a simple central gastric cavity, terminal orifice, 

 and imperforate body-wall composed of two closely apposed inner and 

 outer cellular layers, the former one or entoderm being made up of flagel- 

 late cells, corresponding with those of the ciliated chambers of the ordinary 

 Spongida, and the outer or ectoderm being constructed out of coalescent 

 non-ciliate cells, and in all ways corresponding with his so-called syncytial 

 element of the more complex sponges. No spicula or other endoskeletal 

 structures were secreted by these Haliphyscinata, but the external layer or 

 " syncytium " possessed the faculty of appropriating and building up a 

 variously modified and protective test, or exoskeletal covering, out of sand- 

 grains, sponge-spicules, or any other suitable adventitious particles found 

 in its vicinity. For the reception of the various types described the new 

 group-title of the Physemaria was created, its members being announced 

 by Haeckel to belong properly neither to the sponges nor to the zoo- 

 phytes, but to represent in themselves an independent order which more 

 nearly approached the hypothetic root-form of all Metazoa, his so-called 

 " gastraea," than any yet discovered organic type. 



The various species, five in all, referred to the genus HalipJiysema were 

 severally distinguished by the form and composition of their respective 

 tests or exoskeletal elements, one among these, H. glohigerina, being 

 specially remarkable in having its test built up entirely of the shells of 

 Rhizopods, such as Glohigerina, Rotalia, Orbulina, Textnlaria, and various 

 Radiolarians, collectively indicative of a deep-sea habitat. A second generic 

 group was referred by Haeckel to the Physemarian order, under the 

 new name of GastropJiysema. Of the two species referred to this genus 

 the one received the title of GastropJiysema ditJialamium, while the other, 

 G. seopiila, was identified with an organism described by Mr. Carter in the 

 year 1870 under the name of Squamulina scopula, and referred by that 

 investigator to the group of the Foraminifera. The only essential external 

 difference presented by GastropJiysema, as compared with HalipJiysema, was 



