ACALEPH^. 157 



Family VesiculabiiDj^ -, genera, Vesicularia, Serialaria, Valkeria, 

 Bowerbankia, Family Crisiid^^ ; genera, Crisia, Notamia, An- 

 gmnaria. Family Tubuliporid.e ; genera, Tubulipora, Disco- 

 pora. Family Celliporid^ ; genera, Cellepora^ Lepralia, 3Iem- 

 hranipora. Family Escharibje ; genera, Flustra, Tendra, 

 Cellularia, Retepora, Eschara. Family Alcyonidid^ ; genera, 

 Alcyonidium, Halodactijlus. Family Alcyonellid^ ; genera, 

 Alcyonella, Cristatella, Plumatella, 



LECTUEE IX. 



ACALEPH^. 



In the preceding lecture we saw that, whilst the new individuals pro- 

 pagated by gemmation were, for the most part, like the parent, those 

 that came from the ova were in very few instances like the parent, 

 but underwent a considerable metamorphosis. They quitted the egg- 

 state either as a ciliated planula under the guise of a leucophrys, or 

 were partially ciliated on special lobes, like a rotifer ; or, what was 

 more extraordinary, they came forth under the form of an animal 

 which is usually ranked as a member of a higher class of Radiata, 

 viz., a free-swimming, bell-shaped, or discoid medusa. The laro-er 

 marine animals, so called, are commonly regarded as the typical 

 forms of the class Acalephce, 



This class, the anatomy of which we have now to consider, compre- 

 hends creatures which are amongst the most singular of the whole 

 animal kingdom ; and each additional contribution to our knowledge 

 of their economy adds to the interest, and indeed astonishment, with 

 which the physiologist reflects upon it. 



The Acalephm are remarkable on account of the peculiar nature of 

 their tissues, which are often as transparent as the purest crystal, and 

 seem more like the vitreous humour than any other in the higher 

 classes : they are not less interesting for the elegance of their forms, 

 the beauty of their colours, and for the peculiar property which many 

 of them possess of stinging and inflaming the hand that touches them, 

 whence the name of " Acalei^hae " applied to them by the ancient 

 Greek naturalists, and " sea-nettles " by our own fishermen and 

 sailors. These qualities, being presented by animals which are 

 almost the sole visible representatives of living nature in the wild 



