502 P' E. Keuchenius, 



pletely only about the fine structure of the testes and thus the other 

 Organs of the genitalapparatus are not treated by him. 



My intention in this article is to treat the male genitalapparatss 

 of some Diptera, morphologically and histologically as far as the 

 material at my disposal has enabled me to make out. As this research 

 more especially concerns anatomy, I have passed over spermatogenesis. 

 I have indeed found that in the species examined by me, the earliest 

 stages of spermatogenesis are not to be seen in the adult and conse- 

 quently are already developed in the larva-stage. 



Finally I will not forget to acknowledge my indebtedness to my 

 wife, who with the greatest accuracy and untiring diligence has worked 

 for me and has taken a very great part in the making of the micros- 

 copical sections. 



Method. 



I have studied the male gonads almost exclusively from sections, 

 besides I have dissected some genitalia to compare them also macros- 

 copically. Of course the making of sections has this great advantage, 

 that one can observe the exact Situation of the gonads in the abdomen 

 and one can also find out by what they are surrounded. Besides it 

 is often impossible to dissect the genitalia of smaller species of Diptera. 



For making microtomical sections by Arthropoda already many 

 methods have been recommended by different authors, which methods 

 I cannot all mention, though there are just a few on which I must 

 dwell a httle, in as much as I have made use of them. 



For instance I tried to fix with vom Rath's mixture and that, 

 which was used by Janet (2% picric acid with 95% alcohol) in his 

 researches about Hymenoptera, and I dropped into this Solution 

 the abdomina at the moment, when I cut them off from the living 

 insects. The drawback of vom Rath's mixture was, that the fixation- 

 liquid penetrated with difficulty into the objects, so that the fixation 

 was a failure. Only some of the abdomina sank into the Solution, 

 but most of them remained floating in consequence of the air, which 

 is in the tracheal trunks and the air-cells. To obviate this difficulty 

 I warmed the liquid to from 70 — 75 °C, but also by this means it 

 did not prove to be efficient enough and I have a notion that it in- 

 jured the fixation by the fixation-liquid. The fact is, that in this 

 case the high temperature does the fixing instead of the fixation-liqüid, 

 and a fixation by means of a high temperature, where it concerns the 

 research of the finer histological structure, is an exceedingly censurable 



