74 BULLETIN OF THE 
A corneal hypodermis has been described by Claus (’86, pp. 321, 322) 
in Branchipus and Apus. In Branchipus torticornis, according to Claus, 
the nuclei of the hypodermal cells are arranged around the distal end of 
each cone in circles of six; each nucleus participates in three circles, so 
that there are in reality only twice as many hypodermal cells as there 
are ommatidia. The corneal hypodermis in the eye of Branchipus ver- 
nalis (Plate LV. Fig. 30, nd. h’drm.) is similar to that described by Claus 
in B. torticornis. According to Patten (86, p. 645), a corneal hypoder- 
mis is present in Branchipus Grubii, but the cells, instead of being 
regularly placed, as in either Branchipus torticornis or B. vernalis, are 
stated to be indefinitely arranged. 
The corneal cuticula in Apus is described as unfacetted by Miiller 
(29, p. 56), Burmeister (35, p. 533), Zaddach (’41, p. 46), and Frey 
und Leuckart (’47, p. 205). In Branchipus stagnalis the cuticula is 
smooth according to Spangenberg (’75, p. 30), marked by concavo- 
convex facets according to Grenacher (79, p. 114), and smooth exter- 
nally but facetted internally according to Leydig (51, p. 295). This 
difference of opinion is probably due to the fact that in this species the 
facets are so poorly developed that their form can be determined only 
with difficulty. In Branchipus vernalis, although the corneal cuticula 
is facetted, the facet is not thickened in its centre, but has the form 
of a simple concavo-convex elevation, as described by Grenacher in 
B. stagnalis. In Branchipus paludosus according to Burmeister (35, 
p- 531), in B. torticornis according to Claus (’86, p. 320), and in 
B. Grubii according to Patten (’86, p. 645), the corneal cuticula is 
unfacetted. 
The cone in Branchipus, as Spangenberg (’75, p. 30) first demon- 
strated, is composed of four segments. ‘This observation has since been 
confirmed by Grenacher (79, p. 115), Claus (’86, p. 320), and Patten 
(86, p. 645). In Branchipus vernalis (Fig. 31, con.) the cone, according 
to my observation, consists of four segments. The cellular nature of 
each segment was first clearly stated by Grenacher. Each cone in 
Apus, according to both Grenacher (’79, p. 115) and Claus (’86, p. 321), 
is composed of four cells. 
The vetinula in both Apus and Branchipus consists of five cells. This 
number has been seen in both genera by Grenacher (’74, p. 653) and by 
Claus (’86, p. 319). Spangenberg, however, (’75, p. 31) counted four 
nuclei in the retinula of Branchipus. Since these unquestionably rep- 
resent the nuclei of the retinular cells, and since these cells are usually 
five in number, Spangenberg’s enumeration is probably inaccurate, Pos- 
