107 



two or three lines in length. They are so transparent 

 that one may discern their viscera through their sub. 

 stance, and the blood may be seen to circulate. They 

 have a small, black head, furnished with t\vo pincers, 

 the other extremity is almost square, and much larger 

 than the head. Upon the back may be seen two white 

 streaks, as if they contained ths chyle, these two canals 

 are parallel to each other from the head to the .other 

 extremity, where they come together. In the middle 

 -where the belly and viscera ought to be placed, a 

 blackish matter is perceivable, which has a kind of 

 circulation, sometimes it fills all the body of the worm, 

 sometimes itgathers towards the head or at the other end 

 and sometimes it follows the motion of the animal. This 

 vermicular motion begins atthe posterior extremity,and 

 ends at the head. They have no particular lodge, 

 they walk indifferently into the tubular labyrinth* 

 These sponges are attached to some solid body in the 

 sea. Some kinds are lixed to rocks, others to heaps 

 of sand, or to pieces of petrified matter ; and the sea 

 putting in motion the sand, and the little parcels of 

 broken shells, forces them into the holes of the 

 sponge. 



So far the Doctor. But still I doubt, whether the 

 worms form the sponge, or only lodge therein, though 

 I think the former more probable. 



The same doubt I nave with regard to what fol. 

 4ows, " The Belemnites is a fossilo, a kind of stony 

 shell, which has hitherto perplexed the naturalists of 

 all countries. Strait ones are common in Sweden, 

 Livonia, and Germany, those that are curved are more 

 common in France and England. The nucleus of 

 it seems to be a strait concamerafed shell, which is 

 -surrounded by a huge solid substance. Now how 

 was this formed ? And how is it that some have a 

 nucleus, others not ? Again, how is it, that in some, 

 the cavities containing it, are very small, in others 

 not visible ? 



In order to understand this, we may consider, that 

 Jauy bodies, which we always took for egetable ? 



