482 PHILOSOPHICAL TEANSACTIONS. [aNKO l6g2-3. 



beards or fins of oysters, but were more easily separable from the fish : these 

 strings were thick beset with hairs, continually moving; and through the 

 threads themselves I saw a great number of small animals. 



In the liquor in oysters I found several sorts of animalcules, but in their beards 

 or gills none, possibly because the oysters were dead. 



Observations on the Dissection of a Rat. By Mr. R. W. S. R. S. N° 1 96, 



p. 594. 



The fore-feet of a rat resemble those of the castor. The hair, as in that animal, 

 is also some of it fine, some coarse. The tail scaly, with hairs between every 

 scale, like the castor's ; which shows these two animals have some resemblance ; 

 and indeed the water-rat comes very near the beaver, and makes its holes in the 

 sides of ponds after the same manner. The penis in the rat has a particular 

 passage near the navel, as in squirrels ; and not at the anus, as in the castor. 

 The liver is full of little specks, as large as pins' heads, which are the small 

 glands. There was no gall-bladder, only a ductus felleus ; possibly the bladder 

 was inclosed in the parenchyma of the liver, as it is in some animals. The 

 caecum was much larger than the stomach, and in shape like that of the castor. 

 The testicles lay not behind, but in the groins, on the os pubis. These were 

 like a bottom or skein of thread, rumpled up together, which was visible 

 through the coats of the testicle. This thread continued of near the same size 

 in the epididymides, only towards the deferentia it grew larger. It was tender, 

 and not easy to be unravelled, so that I could not draw out above f of a yard. 

 The prostatas lay under the spermatic arteries. The kidneys were whitish, with 

 their succenturiati. At the neck of the bladder were inserted the vesiculae semi- 

 nales, transparent and filled with the semen. Toward the end of the penis, 

 which had a bony gristle, were two large glands, emptying themselves near the 

 extremity of the penis, and contained a substance like cream, as in the dor- 

 mouse, observed by Swammerdam. 



Fig. 1, pi. 12, represent the parts, viz. A A the kidneys; aa the renes suc- 

 centuriati ; bb the ureters ; cc the crural veins and arteries ; d arteria magna ; 

 e vena cava ; f the bladder ; gg the spermatic vessels, veins, and arteries ; hh the 

 testes, with the branches of the veins and arteries ; ii the epididymides ; kk the 

 deferentia; 1 the penis; m m vesiculae seminales ; nn two glands, from whence 

 a thick juice might be pressed out ; o the balanus. 



