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, 

 tbe 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 IV. Fig. 30, nl. h'drm.) is similar to that described by Claus 

 in B. torticornis. According to Patten ('80, p. 6-15), 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 Midler 

 ('29, p. 5G), Burmeister ('35, p. 533), Zaddach ('41, p. 40), and Frey 

 und Leuckart ('-17, 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. 29.">). 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 Clans ('8G, p. 320), and in 

 B. Grubii according to Patten ('8G, p. G45), the corneal cuticula is 

 unfacetted. 



The cone in Branchipus, as Spangenberg ('75, p. 30) first demon- 

 strated, is composed of four segments. Thus observation has since been 

 confirmed by Grenacher ('79, p. 115), Claus ('8G, p. 320), and Patten 

 ('SG, p. G4.">). 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 ('8G, p. 321), 

 is composed of four cells. 



The retinula in both Apus and Branchipus consists of five cells. This 

 number has been seen in both genera by Grenacher ('74, p. Goo) 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- 



