ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 149 



is important, because it is often stated that the presence of retinulee 

 sharply differentiates ocelli from compound eyes ; but, though absent 

 from lateral ocelli, they are unquestionably present in the median type. 

 To the statement that lateral ocelli are of simple structure, those of 

 the larvae of the Tenthredinidae forming a striking exception. In them 

 the lateral ocelli of the larvae are of complex structure, with retinulae 

 composed of four cells and a typical four-partite rhabdom. The de- 

 velopment of ocelli was studied by the author in Apis mellifica. The 

 first indication of the developing ocellus is a thickening of the epi- 

 dermis, followed by a separation of the cells in the thickened area into 

 two layers. Of these the distal layer forms the crystalline-cone layer, 

 the proximal the retinal layer. As the cells proliferate the epidermis 

 shows an insinking over the developing ocellus. Next there occurs a 

 remarkable separation of the ocellus from the epidermis, which appears 

 to be due to traction exerted by the optic nerve, and results in the with- 

 drawal of the ocellus into the interior of the head. Later, the ocellus 

 again unites with the epidermis, the cells of the latter fusing with the 

 crystalline-cone layer, and forming the so-called iris, as well as probably 

 a part of the lens. 



Simple Eyes of Insects.* — Dr. Richard Hesse, in a preliminary note, 

 states that these can be divided into two groups. First, those without 

 crystalline-cone, without axone or with polyaxonic arrangement of the 

 nerve end-organs ; to this group belong the ocelli of all imagines and 

 of a few larvae. Second, those with crystalline-cone, without axone or 

 with monaxonic arrangement of the nerve end-organs ; such are the 

 ocelli of the larva of Myrmeleo, of caterpillars, and of some other larval 

 forms. In the first group the receptive organs show some variation in 

 structure ; they are simplest in Relophilus ; in Vespa, Apis, and some 

 others rhabdoms are present just as in the compound eyes, each rhab- 

 dom consisting of two rhabdomeres in bee and wasp, of four in Anabolia. 

 Of the second group, the simplest type exists in Myrmeleo, where the 

 individual cells bear at their distal ends a tuft formed of the thickened 

 ends of the neuro-fibrillae, and constituting a peripheral brush (Sti/ten- 

 saum). In the larvae of Sialis each receptive-cell bears a rhabdom. 

 The rhabdomeres are to be regarded as derived from the peripheral 

 brush. In consequence of the above, the compound eyes of insects can 

 no longer be regarded as having originated from ocelli such as those 

 which occur in imagines, but rather from monaxonic eyes with crystal- 

 line-cone of the larval type. 



Insect with Many Eyes.f — Dr. 0. E. Imhof describes a two-winged 

 insect which, in the female, has two pairs of large ocelli and a pair of 

 small ocelli, six in all ; and, in the male, a pair of small eyes, two pairs 

 of large ocelli, and three pairs of small ocelli, twelve in all. It may 

 require a special family ; for the genus the name Polyocellaria is sug- 

 gested. He also says that it may have to do with Ortheria cataphracta. 



Male Genitalia in Coleoptera.J — Dr. L. Bordas finds that, although 

 there appears to be enormous diversity as regards the genital organs of 



* Zool. Anzeig., xxiv. (1901) pp. 30-1. 



+ Biol. Central bl., xx. (1900) p. 527. 



% Ann. Sci. Nat. (Zool.), xi. (1900) pp. 283-448 (11 pis.). 



