230 



LIFE, IN ITS INTERMEDIATE FORMS. 



menciiig at a point far lower than that to which we have 

 ascended in our previous observations, rises in uninter- 

 rupted gradation, though not without many lateral rela- 

 tions, to the very highest type of animal existence. 



If we have been in the habit of picking up sea- weeds 

 from the shore where they have been washed by the 

 waves, or from the little sheltered rock-pools where they 

 delight to grow, we have often seen spread over their 

 smooth fronds what looks like a little piece of muslin, 

 only that it is more delicate, more filmy. It adheres 

 quite firmly to the surface, so that it cannot be rubbed 

 off ; and if we apply our thumb-nail to it, we discover 

 that, thin as it is, the substance of which its subtile 

 meshes are composed is stony or shelly in its nature, and 

 so hard as to scratch the nail. What is it ? It is one of 

 the sea-mats (Membranipora pilosd). 



We bring the magnifying power of a pocket-lens, or a 

 microscope, to bear on it, and our sense of beauty is at 

 once gratified. We see a net- work of glassy cells, each 

 closely resembling a slipper in shape, arranged in the most 

 orderly manner side by side, yet so that the opening of 

 one shall be in contact with the middle of its nearest 

 neighbour, sidewise, while the toe of the slipper touches 

 the heel of the next, lengthwise. The margin of the orifice 

 is a little thickened, like the binding of a slipper, and 

 there are springing up from this rim six short spines 

 which arch over the opening, and a very long one from 

 the front which runs up in the line of the instep. The 

 slipper-like cell is transparent as glass, but in the sub- 

 stance are seen many oval bladders or cavities. 



These cells are so many houses inhabited by active 



