70 SUMMARY OF CURRENT RESEARCHES RELATING TO 



umon« the sperms in the ejaculatory tubes of Melolontha vulgaris, and 

 apparently also the direct results of spermatogenesis. 



Bacteriological Studies in Arthropods.* — M. E. G. Balbiaui finds 

 that saproi^hytic bacilli, when inoculated into the blood, are pathogenic for a 

 large number of Arthropods. Death follows in fi-om twelve to forty-eight 

 hours, according to external temperature, number and origin of spores, 

 size, age, and susceptibility of the subject. They die with all the 

 symptoms which characterize the disease known as "flacherie" in silk- 

 worms, a malady determined by the development of various species of 

 bacteria in the organism. Insects of different orders are not equally 

 susceptible ; those which contain a small quantity of blood in proportion 

 to the mass of the body (Lepidoptera, Diptera, Hymenoptera) are killed 

 more rapidly and surely than those in which the relative proportion of 

 blood is greater, and (above all), in which the blood is richer in corpuscles ; 

 this is specially the case with the Gryllidfe. 



The resistance is due to the corpuscles seizing by their pseudopodia on 

 the bacilli, and to the elements of the pericardial tissue, which seize on 

 and destroy the poisonous organisms. This identity in mode of action is 

 ascribed to the t^enetic relation which exists between the two kinds of 

 cells. Death is delayed if the spores are kept for more than six years in a 

 state of desiccation. 



a. Insecta. 



Spermatogenesis of Beetles.j — Prof. v. La Valette St. George adds 

 a fourth communication to his recent studies on spermatogenesis. He now 

 discusses that of beetles as illustrated by Phratora vitellinse and a few other 

 forms. 



The general facts remain the same, the details alone vary. Primitive 

 sperm-cells, spermatogonia, spermatocysts of spermatocytes, spermatides 

 and spermatozoa follow one another as usual. Recent researches by Gilson 

 and Spichardt are critically referred to. The cellular cyst-skin (" Cysten- 

 haut") round the sixrmatocysts was well seen; it usually contained two 

 nuclei. As usual, the nuclei of the spermatocytes are often divided with- 

 out the pi'otoplasm being divided and rounded off about them. 



In the spermatocyte the neighbour nucleus (accessory nuclear body 

 — " Nebenkern ") appears as a simple thickening of the cytoplasm near the 

 nucleus. It becomes associated with the nuclear contour like the stamp 

 on a signet ring. It exhibits a threadwork structure, as is intelligible 

 from its association with mitosis, sharing in the formation of the spindle- 

 fibres, and representing the residue of nuclear threads after the formation of 

 daughter nuclei. In the spermatide the neighbour nucleus retains for a 

 while its threadwork, bat sends out a fine pi'ocess, the first hint of the 

 sperm. Together with the nucleus it forms the head of the latter. Two 

 threads in the tail were detected. It ai)pears as if both tail and head 

 were ensheathed in a special layer of cytoplasm, while its variable con- 

 tractility presents the different appearances often described. 



Oogenesis of Insects.| — Herr F. Blochmann reports the results of his 

 investigation of the much-discussed oogenesis of insects. His conclusions 

 arc not corroboratory of Will's statements. The young ovum has a large, 

 but not very richly chromatic nucleus. As the ovum enlarges, vacuoles 



* Comptes Hindus, ciii. (1S8G) pp. U52-4. 

 t Arch. f. Mikr. Anat., xxviii. (1886) pp. 1-13 (4 pis.). 



X Festschrift d. Naturh.-Med. Vereins Heidelberg, 1886. Cf. Biol. Centralbl., vi. 

 (1886) pp. 554-t). 



