4XO THE HISTORY OF BIOLOGY 



of a tapeworm that lives in the intestinal canal of the dog — if dogs were 

 fed on coenurus-affected sheep's brains they would infallibly be infected with 

 this tapeworm, which is now called Tania canurus. Through the excrement 

 of the dog the eggs of the tapeworm are scattered about the pastures and 

 thus infect the sheep. In the same way another tapeworm in the dog was 

 traced to bladder-worms in the liver of hares, and a tapeworm in the cat 

 to similar formations in the rat. Again, the large and often fatal liver-para- 

 site echinococcus, which occurs in man, was found to give rise to an almost 

 microscopically small, and therefore hitherto unknown, tapeworm occurring 

 in the dog, the Tania echinococcus , the eggs of which are conveyed, through 

 too intimate contact with the dog, to the human mouth and thence to the 

 intestinal canal. As a result of these researches the knowledge of the intesti- 

 nal parasites, or helminthology, as it had already been termed previously, 

 was placed on entirely rational footing, and it only remained for later ob- 

 servers, by working along the lines laid down by Siebold, to collect fresh 

 facts in order to fill the gaps in the knowledge of the subject. 



Likewise, as regards insect communities, Siebold produced the idea 

 which has since been pursued up to the present time. At first he held with 

 Steenstrup's attempts to explain the reproduction of the bees as a form of 

 alternation of generations, but he realized his mistake, chiefly through col- 

 laboration with a pioneer in the field of practical apiculture, the Roman 

 Catholic priest Johann Dzierzon (1811-1906), of Silesia. He is of course 

 famous as the founder of modern rational bee-keeping, and it was he, too, 

 who, notwithstanding his lack of anatomical training, realized before any- 

 one else the true relationship between the sexes in the community life of the 

 bees. He discovered that the queen-bee is fertilized only once in her life and 

 this while in flight through the air, not inside the beehive, and that the 

 drones are evolved out of unfertilized eggs, while workers' and queen-bees' 

 larvas are developed from fertilized eggs, both having female characters, al- 

 though in the workers they become stunted, owing to lack of nourishment. 

 These important discoveries, upon which Dzierzon based his reform of api- 

 culture, were received with strong opposition on the part of most bee-keepers 

 and would certainly have failed to win general acceptance had not Siebold 

 given them the support of his authority. Already a long while previously 

 (in 1837) he had carried out a careful investigation into the bees' sexual 

 apparatus, with the result that he had discovered the queen's receptaculum 

 seminis; now — at the beginning of the fifties — he placed himself definitely 

 on Dzierzon 's side and by means of a series of experiments and treatises on 

 the subject obtained victory for his views. In connexion therewith Siebold 

 elucidated for the first time the conditions obtaining in parthenogenesis in 

 insects in general, thereby introducing into biological science a field of re- 

 search that, especially in recent times, has aroused keen interest. 



