964 SUMMARY OF CURRENT RESEARCHES RELATING TO 



a. Insecta. 



Regularity of Sperm-movements.* — Following up a previous 

 communication,! Herr J. Dewitz has communicated the results of his 

 further studies on the movements of spermatozoa in finding their 

 way into the ovum. The form investigated was Periplaneta (Blatta) 

 orientalis. 



a. TJie Spermatozoon. The sperms arc seen to he attracted to 

 surfaces, on which they move in circular courses. This was demon- 

 strated in very varied ways with sperms kept in ■ 8-0 ■ 9 per cent, salt 

 solution. In viscid fluids the course was irregular. The direction of 

 motion is always (on the attracting surface) the reverse of that of the 

 hands of a watch. Various interesting modifications of the principal 

 ohservation are noted. 



6. The Ovum. The surface of the ovum, the disposition of the 

 micropyles, &c, are described. The attraction of the sperms to the 

 surface, and the motion in ever slightly varying circles, must obviously 

 secure a speedy entrance into a micropyle. This was successfully 

 verified on hardened empty egg-membranes. Herr Dewitz notes that 

 in many cases what has been referred to as a gelatinous, viscid mem- 

 brane is not really so, and thus offers no hindrance to the movement 

 of the sperms. 



c. In the third division of his memoir Herr Dewitz describes the 

 anatomical relations of fertilization, and shows how they harmonize 

 with what he has observed as to the regular motion of the sperms. 



Blood -tissue of Insects.! — H. Ritter von Wielowiejski finds 

 various kinds of blood-cells in the coelom of insects. The so-called 

 fat-cells have a tendency to unite into larger complexes ; with the 

 exception of some examples of Apis and Melophagns, where there were 

 binucleate, and the imagines of Musca, where there were multinucleate 

 cells, there were only uninucleate cells to be seen. The contents are 

 fluid and fatty, but in a few cases contained albuminous bodies 

 (Coretlira), or uric acid concretions (Lampyridae). The second kind 

 of cell is, in consequence of its colour, called the " cenocyth " ; these 

 were found arranged in groups, or were very small, or formed rows, 

 or plexiform plates, or larger complexes or plates. The third class is 

 formed by the pericardial cells ; these differ so strikingly in the 

 different groups of insects, that it is scarcely possible to give a 

 histological definition of them. Other cells are less easy to find, but 

 may belong to special groups. 



The author is inclined to refer the blood-cells to the secondary 

 endoderm ; as to their function, all that seems certain is that it is 

 not of a respiratory significance. 



Habits of some Guests of Ants.§ — Herr E. Wasmann groups 

 the guests of ants under the three heads of those which stand in 



* Pfliiger's Arch. f. d. gesammt. Physiol., xxxviii. (1886) pp. 358-85 (1 pi.). 

 t See this Journal, ante, p. 43. 

 % Zeitschr. f. Wiss. Zool., xliii. (18S6) pp. 512-36. 



§ Deutsche Eutomol. Zeitschr., xxx. (1886), See Naturforscher, xix. (1886) 

 pp. 269-70. 



