52G SUMMARY OF CURRENT RESEARCHES RELATING TO 



The second rudiment is ectodermal in origin, and arises as an unpaired 

 median structure with a single lumen. The paired ducts which leave 

 this rudiment partly unite to form the unpaired ductus ejaculatorius, 

 while the remainder forms the ectadenia. The fact that the foundations 

 of four testes are laid down points to a close connection between the 

 Scolytidse and the Curculionidae. 



Alimentary Canal of Dytiscidse.* — L. Bordas has studied this in 

 Dytiscus marginalis, Cybistcr rcesclii, Agabus chalconotus, Acilius sulcatum, 

 &c. Although the insects are mainly carnivorous, the length of the 

 gut is very considerable, up to four times that of the body. The 

 gizzard with its teeth and setigerous areas, and the rectal ampulla, are 

 the most characteristic parts. The latter serves as a hydrostatic appa- 

 ratus, as a defensive organ when the animal is out of water, and as a 

 reservoir for excrement in its median and posterior parts. In Agabus 

 the hind-gut enters the anterior extremity of the rectal ampulla, and 

 the caecal portion is rudimentary ; in Dytiscus and Cybister the union 

 is towards the middle of the ampulla; in Acilius it is towards the 

 posterior end, thus leaving a long caecal appendage. 



Chromosomes of Hemiptera Heteroptera.|— Dr. T. H. Montgomery 

 deals with the relations of the chromosomes in the spermatogenesis of 

 species of Tingis, Corixa, Cymus, Lygus, &c, and calls attention to the 

 importance of studying these comparatively in a large number of sjtecies 

 of a group. " By such investigations not only may much of importance 

 be obtained regarding the evolution of cell structures themselves, but 

 by implication a criterion may thereby be obtained for testing genetic 

 relationships." He gives special attention to the " chromatin nucleolus," 

 a term applied to " that peculiar nuclear element which is a chromo- 

 some peculiarly modified in preserving its form and dense structure, 

 which chromosomes, as a rule, show only in the height of mitosis, 

 through every stage of the spermatogenetic cycle." The chromatin 

 nucleoli are interpreted as representing chromosomes on the way to 

 disappearance during progressive evolution. He concludes by express- 

 ing his conviction as to the persistence of the chromosomes from 

 generation to generation in spite of a great amount of metabolic 

 change. 



Taming a Larval Dragon-Fly. } — Frau Maria Sondheim describes 

 the behaviour of a larva of JEschna grandis in her aquarium. It learned 

 to take flies from her fingers held just under the surface of the water ; 

 it even crept on to a finger and devoured its fly while sitting there ; it 

 followed its keeper's movements, and used to remain stationary for an 

 hour or so close to the glass side of the aquarium with its head turned 

 towards her. The pet was unfortunately lost at the time of pupation. 



Peculiar Glands in Trichoptera Larvae. § — Andreas Martvnow de- 

 scribes a remarkable series of unicellular glands, found in Phryganea 

 varia and other larval Trichoptera, in pairs from the second thoracic 

 to the ninth abdominal segment. The glands open to the exterior by 



* Comptes Rendus. exxxii. (1901) pp. 15S0-2. 



t Proc* Acad. Sei. Philadelphia. 1901. pp. 261-71 (1 pi.). 



J Biol. Centralbl.. xxi. (1901) pp. 317-9. 



§ Zool. Anzeig., xxiv. (1901) pp. 449-55 (5 figs.). 



