2 M. E. Hackel on the Organization of Spojiges, 



Placing at the head of them, as is customary, the name of 

 Aristotle, even this " father of natural history" was quite in 

 doubt as to the natm-e of the sponges ; for while, in many 

 passages, he describes the sponges known to him as animals, 

 he regards them in another place as plants, and in a third 

 refers tliem to those indifferent organisms which constitute the 

 gradual and imperceptible transition from the animal to the 

 plant. 



Linn^, who regarded all the sponges known to him as spe- 

 cies of a single genus, Spongia^ placed them, in 1735 (in his 

 ' Systema Naturaj '), at the end of the vegetable kingdom, be- 

 loAv the lowest Cryptogamia, combining them with the corals 

 and coralliform Bryozoa as Lithophyta. Even in the tenth 

 edition of his 'Systema Naturae' (1760) this view is main- 

 tained. But in the twelfth edition (1767) he adopts the views 

 of Ellis and Pallas, who had in the meanwhile declared the 

 sponges to be animals, and placed them with the corals, among 

 the Zoophyta. 



Of those naturalists who even subsequently regarded the 

 sponges as plants, Spallanzani, Sprengel, and Oken are espe- 

 cially to be noted ; and this opinion has been held, even up to 

 the most recent period, by Burmeister and Ehrenberg. Never- 

 theless the sponges have pretty generally passed as animals 

 since Grant, in 1826, thoroughly described the canal-system 

 of the sponges with its "pores" and "oscula," and also ascer- 

 tained their reproduction by means of ciliated free-swimming 

 larv£B. 



With regard to the position occupied by the sponges in the 

 system of animals, two different vicAvs especially stand at pre- 

 sent in opposition to one another, and have done so for more 

 than twenty years. In conjunction with Cuvier, most zoolo- 

 gists i-egarded the sponges as the nearest allies of the corals or 

 polypes, and referred them, with these, to the primary divi- 

 sion of the Radiata. The determining motive for this posi- 

 tion was not, however, the recognition of the actual agreement 

 of the sponges and corals in their most essential characters of 

 organization, but rather the external similarity which exists 

 between many sponges and corals in outward habit, and espe- 

 cially in the mode of stock-formation. But when, about a 

 quarter of a century ago, it began to be perceived that the so- 

 called " Radiate type" was a confusedly mixed assemblage of 

 very various lower animals, and when, afterwards, as the re- 

 cognition of their differences of organization advanced, the 

 Radiata were divided into the three quite different main groups 

 of the Echinodermata, Coelenterata, and Protozoa, the sponges 

 were not left with the corals or Anthozoa among the Coelen- 



