ZOOLOGY AND BOTANY, MICROSCOPY', ETC. 41 



Lygocerus Hyperparasite of Aphidius. — Maud D. Haviland 

 (Proc. ( 'ambridlje Phil. Soc, 11)20, 19. 21K5-5). Plant-lice are frequently 

 parasitized by certain Braconid:i? of the family Aphidiida% of which 

 Aphidius is a good example. The parasite oviposits in the hfemocade 

 of the aphis, and the larva, during development, consumes the viscera of 

 the host. At metamorphosis nothing remains but the dry skin, ^vithin 

 which the Aphidius spins a cocoon for pupation. At this stage the 

 Aphidius itself is apt to be parasitized by certain Cynipida3, Chalcidje 

 and Proccotrypidffi. Thus the Proctotrypid Lygocerus testacdmamis 

 Kietf. is a hyperparasite of AjJhidius salicis Hal., parasite of Aphis 

 saliceti Kalt., from the willow ; and L. earner oniKiefi. is ajiyperparasite 

 of Aphidius ervi Hal., parasite of Macrosiplmm urticee, from the nettle. 

 The author communicates her observations on the life-history of these 

 two species. J. A. T. 



Pharyngeal Musculature of Larvae of Dytiscus marginalis.— 



Walter Spey'er (Zoid. Anzeii/., li)20, 51, 248-50, 4 tigs.). A detailed 

 description, in some ways extending that of Rungius (11)11). An 

 analysis is given of the dorsal dilators (eight in number), the ventral 

 dilators, the circular muscle, and the longitudinal musculature. Attention 

 is directed to the bristles borne by the pharyngeal intima and their 

 probable function. J- A. T. 



Synapsis in Cockroach. — Lancelot T. Hogben (Proc. Roy. Soc, 

 11)2U, ]>. 91, ;)05-21», r> pis,). A study of oogenesis and spermatogenesis 

 in Periplaneta. The chromosomes do not divide in the pre-meiotic 

 mitoses, as they pass to the polar ends df the spindle ; in the telophase, 

 they become attenuated before passing into the reticulate condition, but 

 do not display any evidence of cleavage. The splitting of individual 

 chromosomes begins in the prophase, the separation of the halves being 

 a process of progressive differentiation ; cleavage is completed before 

 they adopt the equatorial position in the metaphase. Counts in the 

 metaphase confirm Morse's view that there are two accessory chromo- 

 ■somes in the female cells and an unpaired heterochromosome in the male. 

 'I'he accessory chromosomes in the female behave in all respects like 

 autosomes. 



Hi its earliest stages the heterotype prophase differs from the pre- 

 meiotic reticulate nucleus in the organization of the chromatin in the 

 form of elongated, finely beaded filaments, forming an intricate tangle. 

 The polarized leptotene threads of the early bouquet are present in the 

 full diploid number. Parallel conjugation of leptotene threads takes 

 place in the bouquet stage at the point of masiujal contraction. The 

 diplotene loops of the post-synaptic spireme become straightened and 

 at)breviated, in anticipation of their transformation into heterotype 

 chromosomes. Li both cases two of the bivalents retain their looped 

 condition till the transformation of the remainder has already made 

 considerable ]U"ogress. and it is suggested that the differential rate of 

 metamorphosis of annular heterotype chromosomes has given rise to the 

 appearance that the latter are foimed through the union of the free ends 

 of a diplotene loop. The heterotype chromosomes are formed by the 



