Remay^hs on the Descent of Animals. _ 139 



bodily form, with its coarser distinctive marks, varies beyond the 

 limits of the so called species and genera ; and that, with like 

 external habits, the internal particles which we looked upon as 

 specific, are transformed into others, as it were under our hands." 

 "Any one," thus concludes this section of Schmidt's work on the 

 Fauna of the Atlantic Sponges, " who with regard to sponges, 

 makes his chief business the manufacture of species and genera, 

 is reduced ad ahsurdum, as Hseckel has shown with exquisite irony 

 in his Prodrome to the Monograph in the Calcareous Sponges." 



" In my specific researches," continues Schmidt, " I confined 

 myself essentially to the siliceous sponges, and by thousands of 

 microscropic observations, by measurements, by drawings, by 

 facts and inferences, have produced evidences, which acute oppo- 

 nents of the immutability of species had not brought forward 

 before me, that in these sponges, species and genera, and conse- 

 quently fixed systematic unities in general have no existence. 

 The other division of the same class, the calcareous sponges, had 

 been treated with unrivaled mastery by Haeckel in his mono- 

 graph." 



Haeckel was not only able to confirm Oscar Schmidt's state- 

 ments, " but, owing to the smaller compass and the greater facil- 

 ity of observing the groups selected for study, to advance with 

 more sequence and continuity, from the observation of details to 

 the whole, to portray its morphology, physiology, and evolution- 

 ary history, with the utmost completeness." He sums up his. con- 

 clusions as follows : (Preface to American Edition of History of 

 Creation, p, 15.) " For five consecutive years I have investigated 

 this small but highly instructive group of animals in all its forms 

 in the most careful manner, and I venture to maintain that the 

 monograph, which is the result of these studies, is the most com- 

 plete and accurate morphological analysis of an entire organic 

 group, which has up to this time been made. Provided with the 

 whole of the material for study, as yet brought together, and as- 

 sisted by numerous contributions from all parts of the world, I 

 was able to work over the whole group of organic forms, known 

 as the Calcareous Sponges, in the greatest possible degree of full- 

 ness, which appeared indispensable for the proof of the common 



