ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



Development of Polyembryonal Chalcidians.* — Friedrich Martin 

 publishes a paper on the development of the polyembryonal Ohalcidian 

 Ageniaspis fuscicollis Dalm, which is parasitic on Hyponomeuta cognatella. 

 Ageniaspis fuscicollis lays its eggs within the eggs of its host, which adhere 

 in packets of 20-40 to the bark of the Euonymus on which Hyponomeuta 

 feeds. The caterpillars emerge in autumn but remain hidden till spring 

 when they begin to feed. The Ageniaspis eggs have by May developed 

 to " Keimschlauche " within them, and go through the pupal stage at 

 the same time as the host. They leave their pupal covering some time 

 after the butterflies emerge, and they are then ready to infect the new 

 generation of eggs. The investigator finds that the ovarian tubes of 

 Ageniaspis are typically polytrophic in the anterior part, but in the 

 extended posterior part they contain free follicles. The germinal vesicle 

 of the developing egg shows first a polar aggregation and then a regular 

 distribution of chromatin substance ; this then breaks up, and forms 

 numerous chromatin corpuscles which unite to form apparently four 

 chromosomes lying parallel to the longitudinal axis of the ovum ; finally 

 these again unite into a compact body. In regard to maturation, 

 division, and the fate of the polar bodies, the investigation confirmed 

 the results reached by Silvestri, and amplified them in some particulars : 

 the early differentiation of trophamnion and blastomeres ; the complex 

 transformation of the polar bodies ; the differentiation of the plasma of 

 the trophamnion into an inner mass and an outer zone. The nucleolus 

 of Ageniaspis presents certain characteristics that mark it off from other 

 known structures, such as yolk-nuclei, within the ooplasm. It arises in 

 the posterior part of the young ovarian egg, grows within it, is labile 

 and vacuolar during the process of maturation, is taken up into one of 

 the two first blastomeres, the division of which it inhibits, then under- 

 goes progressive degeneration until, at the 4-celled stage, it is no longer 

 demonstrable. The ova of Ageniaspis can only develop in the em- 

 bryonic cells of Hyponomeuta : those that lie within the yolk undergo a 

 characteristic process of degeneration. Occasionally the trophamnion 

 plasma of the polyembryo was found filled with bacteria-like structures 

 which may have come from the caterpillar-host. The second chitinous 

 envelope of the Hyponomeuta-egg encloses it completely. 



5. Arachnida. 



Second Pair of Lung-books in Mygalomorph Spiders.* — B. Haller 

 maintains that these are derivable from the tufted tracheae of Pro- 

 tracheate spiders (Dysderidee, Aryyroneta). He found, for instance, that 

 in Mygale a long tubular trachea arises from each of the posterior lung- 

 books and extends far forward in the cephalothorax. From a study of 

 the development of the lung-books or plaited trachea3 in Gmlotes atropos, 

 Haller confirms his view that the so-called lung-books are comparable to 

 tufted trachea? and not to Crustacean gills. Arachnoids are to be traced 

 back to Tracheata, not to Xiphosura. 



* Zeitschr. wiss Zool., ex. (1914) 419-79 (2 pis. and fi figs.). 



t Arch. Mikr. Aiat., lxxxiv. (1914) lte Abt.. pp. 438-45 (3 fiefs). 



Oct. 21st. 1914. 2 h 



