182 THE MICROSCOPE. Dec. 



Cockroaches are unisexual. The male and female differ 

 slightly. The male has two styles (figs. 6 and 7, t) at- 

 tached to tlie ventral hind margin of the ninth abdominal 

 somite. The female ai)pendages are boat-sha^jed and 

 are attached to the seventh somite. 



The female develops egg capsules each of which car- 

 ries sixteen eggs (fig. 10). These oblong capsules are 

 carried by the mother and ultimately layed by her. The 

 young then emerge and are helped out of the egg and of 

 the capsules by the mother. 



The cockroach and its allies do not undergo that meta- 

 morphosis which is generally characteristic, of insects. 

 The larva or young-only differ from the adult by being 

 paler in color and having no wings. It undergoes from 

 five to seven sheddings of the skin. At last ecdysis or 

 skin shedding of the wings appears. 



The fads contained in this article are from Edward 

 Aveling's article in the English Mechanic. 



The Preparation of Diphtheria Antitoxic Serum. 



By H. K. MulFord. 



The discovery of diphtheria antitoxin was made by 

 Behring, as a result of his primary and original investi- 

 gation in connection with Kitasato upon tetanus antitoxin. 



The method of preparation first proposed was the in- 

 jection into suitable animals of cultures of the dip'heria 

 bacillus in which the bacilli had been killed by heat. 

 When the animal could stand these and manifest only a 

 slight irritation or ofdena at the point of injection or by 

 showing only feeble temperature reaction, highly attenu- 

 ated living cultures were introduced in increasing 

 amounts, a sufficient immunization or resistance being 

 given by the primary injection to prevent fatal termina- 

 tion. The injection of living cultures, however, are 



* Read at Montreal before the A. Ph. A. 



