72 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
nothing to do with the formation of the sexual products. The present 
author entirely agrees with Toyama. The spermatic tubes at an early 
stage consist of a mass of spermatogonia. One of these in each tube 
becomes specialised to form Yerson’s cell; the others form spermatocytes 
and ultimately spermatosomes. Quite similar appearances can be seen 
in the ovarian tubes. Yerson’s cells are probably both supporting and 
nutritive. 
Defensive Adaptations of Lepidopterous Larvae.* — Mr. H. G. Willis 
gives a vivid account of many of the more or less familiar instances of 
these adaptations. 
Abdominal Appendages of Insects | — Dr. E. Heymons criticises 
Yerhoeff’s conclusions as to the appendicular nature of the genital parts 
in insects. Yerhoefft rested his argument mainly on the indubitable 
appendage nature of the copulatory parts in Myriopods, on the occasional 
jointing of the genital structures, and on the musculature. To these 
arguments Heymons entirely objects : — (1) One cannot argue from the 
copulatory legs of Julus or Lithobius to the analogous structures in 
insects. (2) Their jointing is not a proof of genuine appendicular 
nature. (3) The argument from musculature is also illegitimate. 
Arctic Lepidoptera.§ — Dr. A. Pagenstecher gives an account of what 
is known in regard to Arctic Lepidoptera. They are characterised by 
their thick covering of hair, pale transparent colouring, great variability, 
long larval period, and great power of resistance to cold. There is a 
general, but by no means complete, resemblance between the northern 
and the Alpine fauna ; thus the characteristic Alpine genus Parnassius 
is almost absent in the north. 
Internal Metamorphosis of Ants.|j — Herr W. Karawaiew has 
studied this in the female larvae of Lasius flavus, particularly as regards 
the gut and the musculature. There is no metamorphosis as regards 
nervous system, tracheae, or heart. The most remarkable feature is 
the entire absence of phagocytosis. Disintegration and chromatolysis 
occur, but phagocytes play no part — a fact which may be associated 
with the long duration of the metamorphosis in ants. 
Development of Gut in the Silk-Moth.lf — Sig. E. Yerson notes the 
following results. The mid-gut of Bombyx mori is never a dosed sac ; 
the epithelial cells of fore-gut and hind-gut do not multiply after the 
beginning of the larval period, they merely grow ; the fully formed 
epithelial cells of the mid-gut remain of the same size in all the larval 
periods, and lose their power of dividing ; they are all able to secrete, 
but are not all alike chemically ; they and the goblet-cells to which 
they give rise have a strictly limited length of life. There are, however, 
nests or centres of epithelial regeneration where abundant proliferation 
occurs before each moult ; at the base of the cardiac and of the pyloric 
valve there is a germinal ring which proliferates at each moult, and 
enlarges the valves; the firm membranous sheath which forms a sort 
* Trans. Manchester Micr. Soc., 1896, issued 1897, pp. 61-72. 
t Zool. Anzeig., xx. (1897) pp. 401-4. J Tom. cit., pp. 293-300. 
§ JB. Nassau Ver. Naturk., 1. (1897) pp. 179-240. Zool. Centralbl., iv. (1897) 
pp. 795-6. 1| Zool. Anzeig., xx. (1897) pp. 415-22. ^ Tom. cit., pp. 301-2. 
