vii HISTORY 167 



of a Plant, ... So that a Sponge, instead of being a Zoophyton, 

 is but the one-half of a Plant." 



Sponges figure in herbals beside seaweeds and mushrooms, 

 and Gerarde says : l " There is found growing upon rockes near 

 unto the sea a certaine matter wrought together of the foame 

 or froth of the sea which we call Spunges . . . whereof to speak 

 at any length would little benefit the reader . . . seeing the 

 use thereof is so well known." About the middle of the eighteenth 

 century, authors, especially Peyssonnel, suggested that sponges 

 were but the houses of worms, which built them much as a bee or 

 wasp builds nests and cells. This was confuted by Ellis in 1 7 6 5 , 2 

 when he pointed out that the sponge could not be a dead structure, 

 as it gave proof of life by " sucking and throwing out water." 

 To Ellis, then, is due the credit of first describing, though im- 

 perfectly, a current set up by sponges. He mentions that Count 

 Marsigli 3 had already made somewhat similar observations. 



It was not till 1825 that attention was again turned to the 

 current, when Eobert Grant approached the group in a truly 

 scientific manner, and was ably supported by Lieberktihn. It 

 would be impossible to do justice to Grant in the brief summary 

 to which we must limit ourselves. The most important of his 

 contributions was the discovery that water enters the sponge by 

 small apertures scattered over the surface, and leaves it at certain 

 larger holes, always pursuing a fixed course. He made a few rough 

 experiments to estimate the approximate strength of the current, 

 and, though he failed to detect its cause, he supposed that it was 

 probably due to ciliary action. Grant's suggestion was afterwards 

 substantiated by Dujardin (1838), Carter (1847), Dobie (1852), 

 and Lieberkiihn (1857). These five succeeded in establishing 

 the claims of sponges to a place in the animal kingdom, claims 

 which were still further confirmed when James- Clark 4 detected 

 the presence of the protoplasmic collar of the flagellated cells 

 (see pp. 171, 176). Data were now wanted on which to base 

 an opinion as to the position of sponges within the animal 

 kingdom. In 1878 Schulze 5 furnished valuable embryological 

 facts, in a description agreeing with an earlier one of Metschni- 

 koff's, of the amphiblastula larva (p. 226) and its metamorphosis. 



1 Gerarde s Herbal, enlarged and revised by Thomas Johnson, 1636, p. 1587. 



- Phil. Trans, lv. p. 280. 3 Histoire Phys. de la Mer, 1725. 



4 Mem. Boston Soc. i. 1867, p. 305. 5 Zeitschr. wiss. Zool. xxxi. 1878, p. 262. 



