148 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tercalary) segment, and the mandibular, maxillary, and labial segments ; 

 bat Janet raises the total to nine by analysing the acron into four somites. 



Mouth-parts of Insects.* — J. W. Folsom has studied the develop- 

 ment of the mouth-appendages of Anurida maritima, a member of the 

 Collembola, with a view especially of determining the homologies of 

 these structures in the different Arthropods. He finds that the antennae 

 of Hexapoda are equivalent to the antennules of Crustacea and to the 

 embryonic praeantennae of Chilopoda. In the embryo of Anurida and 

 the adults of certain Apterygota, rudimentary premandibular appendages 

 occur, which represent the second antennae of Decapod Crustacea, and 

 probably the antennae of Diplopoda and Chilopoda. They belong to an 

 intercalary segment which, from its distinct ganglion, must be regarded 

 as one of the primary bead-segments. The hypopharynx in Apterygota 

 consists of two superlinguae and a lingua which originates independently. 

 The superlinguae correspond to a distinct segment, and are the homo- 

 logues of the first maxillae of Malacostraca and Chilopoda, while the 

 maxillaB in Insects are the homologues of the second maxillae in these 

 groups. In Anurida the labium developes essentially as in Pterygota, 

 and is homologous with the first maxillipeds of Crustacea. In conse- 

 quence, including the ocular, intercalary, and superlingual segments, the 

 author finds that the head in Anurida consists of seven segments, as it 

 probably does in all Insects. 



(Enocytes of Insects.f — Sig. Enrico Verson points out that Koschev- 

 nikow, in his recent (1900) paper on these cells in the hive-bee, has 

 overlooked Verson's earlier work on the similar cells in JBombyx mori. 

 The " hypostigmatic gland-cells " of Yerson are identical with the 

 " larval cenocytes " of Koschevnikow, his " epigastric gland-cells " with 

 the " imaginal cenocytes " of the latter. As common characters the two 

 kinds of cells have (1) their origin from the hypodermis, and (2) the 

 fact that both produce a visible secretion. They differ from one another, 

 apart from the primary difference in size and position : — (1) in the time 

 of appearance, the hypostiguiatic glands appearing in the egg and the 

 epigastric at tho time of pupation ; (2) in that while the former do not 

 increase in extra-ovular life, the latter multiply by amitotic division 

 during pupation ; (3) in the shape of the nuclei, those of hypostigmatic 

 cells being branched and those of the epigastric rounded. These con- 

 clusions are compared with Koschevnikow's statements as to the origin 

 and relations of the two kinds of cell. 



Structure of Ocelli. :J — W. Eedikorzew has studied the ocelli in the 

 larvae and imagines of a number of insects, and finds that, according to 

 their position on the vertex or on sides of the head, they may be divided 

 into two sets. The difference in position corresponds to a difference 

 in structure ; for while the lateral eyes contain few cells and are of 

 relatively simple structure, those on the vertex are much more complex. 

 A complexity of considerable importance is that in the latter ocelli the 

 retina cells are united in groups of two, three, or more, each group 

 forming a retinula which is furnished with a typical rhabdom. This 



* Bull. Mus. Comp. Zool. Harvard, xxxvi. (1900) pp. 87-157 (8 pie.). 



t Zool. Anzeig., xxiii. (1900) pp. 657-61. 



% Zeitsohr. wiss. Zool., lxviii. (1900) pp. 581-624 (2 pla. and 7 figs.). J 



