Part second. 



Siphonophora. 



These, among the most wonderful of the inhabitants of the 

 sea, are at once the dehght and the despair of the naturahst. For 

 the wonderful form and beauty of their body is associated with 

 such delicacy, that it breaks to pieces at the slightest touch. Never- 

 theless, the fact that, especially in calm weather, specimens of 

 Physophora (fig. 89), Forskalia (fig. 92), Hippopodius (fig. 90) and 

 others may be seen in the Aquarium is due to the particular care 

 used in their capture (see p. 58). But it will easily be understood 

 that it cost much more trouble and countless experiments before 

 a successful method was found of preserving these "noli me tangere" 

 so that they could be put up in alcohol and sent to the zoological 

 museums. 



The Siphonophora are looked upon by most naturalists as free 

 swimming colonies, that is to say, creatures which consist of more 

 than one individual, yet together form a single unit. It is not 

 rare to find individuals of one species thus united; the corals 

 form one of the most striking examples. The case of the Siphono- 

 phora, however, is somewhat different: for, while all the individ- 

 uals of a colony of corals are built up on the same plan, so that 

 each has the same functions and would be able to continue its 

 life alone, the colonies of Siphonophora are composed of very 

 differently formed individuals (polymorphs) which divide among 

 themselves the different functions of the colony. Special nutritive 

 polypes undertake the nutrition of the colony; special bell-shaped 

 individuals, like medusse, perform the swimming movements; 

 true medusae are charged with the reproduction. In short, we 

 have a "division of labour" taking place as it does among the ants 

 and bees ; but with this difference, that among them the polymorph 

 individuals (the workers, drones, queen) are separate one from the 

 other, whereas in the Siphonophora they are inseparably united. 



For the most part the Siphonophora colonies are drawn out 

 lengthways (e. g. Forskalia, fig. 92) and the single individuals 

 are then arranged as if attached to a long thin string. On the 

 other hand in the beautiful blue Sallee Man, Velella (fig. 91), 

 this common stalk is replaced by a wide stiff disk overshadowing 

 all the polypes and bearing on its upper surface a triangular crest, 

 which catches the wind like a sail and enables the colony to drift 

 along on the surface of the water. 



In all groups of marine animals, from these simple ones up to the 

 fishes, we find kinds, the colours of which compete with those of tropi- 

 cal birds and butterflies in splendour and variety. And so — a com- 

 passionate reader will think, on reading in another place (p. no) 

 of the deafness of the sea-beasts — these poor creatures are com- 

 pensated for the lack of one sense by the joy at the sight of their 

 gloriously coloured companions: for all these tints are naturally 



