2 M. E. Hackel OJi the Organization of Sponges^ 



Placing at the head of tliem, as is customary, tlie name of 

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

 doubt as to the nature of the sponges ; for while, in many 



f)assagcs, he describes the sponges kno^\^l to him as animals, 

 16 regards them in another place as ])lants, and in a third 

 refers them to those inditiercnt organisms which constitute the 

 gradual and imperceptible transition from the animal to the 

 plant. 



Linne, 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 ot the vegetable kingdom, be- 

 low the lowest Ciyptogamia, combining them with the corals 

 and coralliform Bryozoa as Lithopliyta. Even in the tenth 

 edition of his 'Systema Natura3 ' (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 tlieir reproduction by means of ciliated free-swimming 

 larva\ 



With regard to the position occupied by the sponges in the 

 system of animals, two different views 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 regarded the sponges as the nearest allies of the corals or 

 polypes, and refen-ed them, with these, to the primary divi- 

 sion of the Radiata. The detennining 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 es]3e- 

 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, Calenterata, and Protozoa, the sponges 

 were not left with the corals or Authozoa anion a; the Coelen- 



