VOL. XXII.] PHILOSOPHICAL TRANSACTIONS. 541 



Further Observations on the ^nimalcula in Semine Masculino. By M. Ant. 

 Leuwenhoeck, F.R.S. N° 268, p. 739. 



Having procured from a butcher the testicles of a young ram, as soon as 

 killed, when only between 4 and 5 months old, I opened the seminal vessel that 

 lies without upon the testicle, from whence I took out the seed, which to the 

 naked eye appeared white, and viewing it with my glass, I observed an unspeak- 

 able number of living creatures in it, swimming in the liquor in vast shoals to- 

 gether, some steering the same course, then by thousands at a time breaking 

 off from one company, and joining themselves to another; in short, the strange 

 and wonderful swimming of these creatures is impossible to be described. — I 

 placed also some of the seminal vessels before the microscope, to discover, if 

 possible, the creatures living therein ; but could pot discover any thing of it. 

 I followed the vasa deferentia till I brought them to their joining with the 

 adferentia, in which vessels I found a vast number of these worms, but none 

 living. Next, I opened the testicle into which these vessels went, but could 

 not discover in the least any of these creatures in the seed ; but instead thereof 

 I saw a great many bubbles or bladders, some as large as those worms, and 

 some less. 



The next morning early I opened again some of the seminal vessels, near the 

 place where I had opened the others the day before, and found them as lively as 

 at the first ti;ne ; but when I continued the same observations about noon, I 

 could not perceive that any of the worms were living. The like experiments 

 were afterwards repeated. 



There is a gentleman, who boasts that he was the first that ever discovered 

 these creatures, by the help of a microscope ; but he is mistaken, for he owns 

 that his first discovery was in the year 1678 ; whereas I not only gave the Royal 

 Society an account of the same, in Nov. 1077 ; but even 3 or 4 years before, 

 at the request of Mr. Oldenburg, I had made an enquiry into those matters. 



Fig. 19, pi. 12, exhibits a group of these animalcules, in different postures, 

 as magnified by the microscope. 



It is well known to many, that my hypothesis is, that every one of these in- 

 cludes a lamb ; yet after they are nourished and enlarged in the belly of the fe- 

 male, they soon put on the same shape. But this is not strange, as we find by 

 experience in a worm or maggot, in which, after it is come to its full growth, 

 whether we dissect it, or examine the outside only, we find none of its parts 

 like those of a fly ; and that all these creatures, a little before their transmu- 

 tation, lie as. still as if they had no life in them; and a few hours after their 

 change, they shut themselves up in a skin or shell, which we call a popje or 



