NATURE AND AFFINITIES OF THE SPONGES, 1 6 



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and in that case amazingly remarkable isomorphism, the erasure of their 

 names from scientific nomenclature, and also that of the entire Physema- 

 rian order, will be rendered unavoidable. Most unfortunately for Professor 

 Haeckel, the context of his essay under discussion upon the gastrxa theory 

 in general, and upon the group of the Physemaria in particular, so abounds 

 with direct negations and manipulations of known facts in order to adapt 

 them to the requirements of his own hypotheses, that the verdict arrived 

 at by the most impartial students of this question must inevitably tend to 

 cast discredit upon his representations even where the same are possibly 

 correct. It is thus not a little surprising to find reproduced as the larval 

 type of HalipJiysema in this essay, the self-same erroneous accounts and 

 diagrammatic illustrations of his so-called " gastrula-larva " of the sponges, 

 first formulated in his ' Monograph of the Calcispongiae,' and submitted at 

 page 157 of this volume. 



The same inversion of the anterior and posterior apices and accompany- 

 ing fallacious allocation of a gastric cavity, oral aperture, and evenly 

 developed external and internal cellular layers, is once more repeated, 

 the larval forms of the Physemaria being made to correspond with a like 

 altogether hypothetic formula. The histologic characters of the essential 

 collar-bearing flagellate cells of the sponge-body, assumed to be shared 

 by HalipJiysema and its allies, are again materially reduced in order to 

 make them conform more nearly to the plan of ordinary tissue-cells, and 

 with the morphologic and functional value of which they are alone accredited. 

 Professor H. James-Clark and Mr. Carter had already shown that these 

 peculiar flagellate sponge-cells exhibited a very significant Protozoic 

 feature in the possession of two or more posteriorly located, rhythmically 

 pulsating, contractile vesicles. In his ' Monograph of the Calcispongise,' 

 Professor Haeckel grudgingly conceded and figured a single posterior 

 vacuole, but denied to it the property of rhythmical contraction, affirming 

 that it was a mere non-persistent and unessential lacuna developed in the 

 protoplasmic substance of the cell. In that advanced exposition of the 

 gastraea theory, however, embodied in his ' Biologische Studien ' for the 

 year 1877, the contractile vesicle, or protoplasmic lacuna, is improved 

 altogether off the morphologic landscape, and the essential flagellate 

 sponge-cell now appears with a simply nucleated but otherwise undiffer- 

 entiated protoplasmic body. In two instances only does Haeckel make 

 any concession to the antagonistic results arrived at by contemporary 

 explorers in the same field of research, while even here these results are 

 with a little tension made subservient to his special views. In the first 

 place, the evidence since adduced not being confirmatory of his diploblastic 

 interpretation of the sponge embryo, as produced by the delamination of 

 the interior from the outer cellular layer, he now declared that essentially 

 the same results were obtained, and the same form constructed, by the 

 process of invagination. In the second place, the researches, more espe- 

 cially, of Oscar Schmidt, having elicited the fact that in many instances 



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