ADDITIONAL NOTES. 



1. The Nature vf Sponges. Page 29 ^ 



1 may fortify my opinion of the vegetable nature of these productions by the 

 following quotation from the " Elements of Physiology" by Muller, the cele- 

 brated professor of anatomy in the university of Berlin " If, therefore, it is 



still a matter of doubt whether certain simple organized beings, such as the 

 sponges and several so called alcyonia, are animal or vegetable, the absence of 

 all voluntary motion in these bodies, whether of the whole or of individual parts 

 of it, must determine the question, and they must more properly be numbered 

 among the vegetable marine structures. It may certainly be said that the embryo 

 of sponges, as Dr Grant has shown, like the embryo of polypes and corals, 

 moves by means of cilia ; but the distinctive marks between the embryo of 

 sponges and marine infusoria are by no means certain, and similar motions have 

 been many times observed in the embryo of true vegetables, — of the alga, for 

 example." p. 42. Lond. 1837. 



Mr J. Hogg, hi a letter dated June 25, states that the green colour of the fresh 

 water sponge (Spongilla fluviatilis) depends upon the action of light, — as he has 

 proved by experiments which shewed that pale coloured specimens became green 

 when they were exposed, for a few days, to the light and full rays of the sun ; 

 while on the contrary green specimens were blanched by being made to grow in 

 darkness or shade. Hence Mr H. infers the vegetability of this sponge ; but he 

 still leans to the opinion that the sea sponges are animals. 



Dujardin, again, is a new advocate for the animality of all sponges ! " M. 

 Dujardin having repeated his observations on spongillse or fresh water sponges, 

 as well as others on marine sponges, thinks he has proved, that these ambiguous 

 beings are positively groups of animals, capable of contraction and extension. 

 If a piece be detached from a living sponge, and submitted to a microscope, it 

 will be seen to groupe itself into irregularly rounded masses, and change the 

 form of its edges incessantly : isolated portions, detached from the general mass, 

 move slowly in the liquid, and creep along by means of their alternate contrac- 

 tion and expansion." Athenaeum, June 16, 1838, p. 430 I may remark on 



these experiments, that locomotion is no proof of animaUty. Several algce are 

 locomotive. 



2- The asexual character of Zoophytes. Page 46. 

 This is contrary to the opinion of Professor Wagner. He says that double- 

 ness of sex appears to be an invariable condition of all animals ; and when the 

 sexes are not separate individuals, there always exists a hermaphroditical organ- 

 ZHtion. He has discovered masculine organs in the Actinice. " I found, last 

 Autumn," he says, " in the isle of Heligoland, upon the Actinia holsatica and rufa 



