Life-history of Phalacrocera replicata. 349 
A striated hem (fig. 23) is present in the epithelium of 
the stomach, though it 1s often demonstrated with diffi- 
culty. The hem consists of close-set, short, and blunt 
processes, which superficially, at least, resemble the per- 
forated (7) end-plates of the epithelium of the villi in 
Vertebrates. 
The epithelium is regenerated by small cells at the 
base (fig. 23), which are often grouped in twos and 
threes (Watney’ s buds).* 
A peritrophic membrane t is found here as in some 
(perhaps many) other Dipterous larve. It is a secre- 
tion of the epithelium, which encloses the food and 
keeps it from direct contact with the epithelium. In the 
Chironomus larva it is particularly firm and homogeneous, 
forming a distinct tubular membrane. In the Dicranota 
larva what appears to be the same thing is voluminous 
and irregular.{ We think it probable that the peri- 
trophic membrane originates in the protrusions described 
above. It persists throughout the stomach and a great 
part of the intestine. It is a singular circumstance that 
the peritrophic membrane should arise in quite different 
fashions in different insects. In the Chironomus larva, 
and probably in Lepidopterous larvee, it is a perpetually 
renewed prolongation of the chitinous lining of the 
stomodeum ; in Myriopods, various Dipterous larve, 
including Phalacrocera, and other insects, it seems to be 
a secretion of the epithelium of the stomach (Balbiani, 
loc. cit., pp. 30-32). We can confirm Balbiani’s account 
so far as relates to Chironomus. 
The epithelium gradually changes its character in the 
different parts of the stomach. Near the cesophageal 
invagination it is slightly folded, and consists of tall, 
columnar cells, grouped in bundles. Protrusions and 
** Watney, Phil. Trans., 1877 ; Miall and Denny, The Cock- 
roach, p. 122 (1886); Oudemans, Bijdrage tot de Kennis der 
Thysanura en Collembola, p. 54 (1887) ; Balbiani, Joc. cit., p. 54 
(1890). 
+ The name is Balbiani’s (oc. czt., p. 32). The same author 
gives references to Plateau, Schneider, and other naturalists, who 
have described a membrane enclosing the food in the intestine. 
See also Cuénot, Etudes physiol. des Orthoptéres, Arch. Biol. (2), 
aN (1896). 
~ I now think that the secretion poured out upon the food in 
the Dicranota larva originates in the stomach. L. C. M 
TRANS. ENT. SOC. LOND. 1897.—PART IV. (DEC.) 24 
