404 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pons of the protoccrcbral lobes is a narrow band of Jotted substance, of 

 a horseshoe shape; by cither end it is united with one of the proto- 

 ccrcbral lobes, and its substance is invested by ganglionic cells. 



The pedunculated body is partially inclosed in the protoccrcbral 

 lobe ; it consists of a calyx, a stalk, an anterior and an internal tubercle ; 

 the cavity of the calyx is tilled with very small nerve-cells, containing 

 but a small quantity of protoplasm. The median protocerebruin is 

 placed below and between the protocercbral lobes, and consists of a 

 central body, a median lobe, two lateral lobes, and the two tubercles of 

 the central body. The dcutocerebrum is situated below the proto- 

 cerebruin, and is composed of two pairs of nervous masses ; it gives rise 

 to four pair of nerves — the antennary, the accessory antennary, the tegu- 

 mentary nerve, and the root of the stomatogastrie ganglion. The trito- 

 cerebrum is formed of a pair of lobes, each of which is placed below and 

 in front of the corresponding dorsal lobe of the deutocerebrum. 



In the second part of the memoir a comparison is instituted between 

 the brain of Insects and that of Crustacea ; * in both there are the same 

 constituent parts, but the protocerebral lobes of Crustacea are widely 

 separated from the median line, and placed in the oculiferous peduncles. 

 As the deutocerebra are similar it follows that the antennary nerve of 

 the Insect is the homologue of the nerve of the antennule of Crustacea. 

 The tritocerebrum of the Insect is, as compared with that of Crustacea, 

 considerably reduced. The nerve of the external antenna is not repre- 

 sented, but the nerves of the labra are homologous. The root of the 

 stomatogastrie ganglion of Crustacea is the homologue of the root of the 

 frontal ganglion of Insects, and the stomatogastrie ganglion of the former 

 is homologous with the frontal ganglion of the latter. M. Viallanes is 

 of opinion that the head of the Insect is formed of three pre-buccal and 

 three postbuccal " zoonites " ; the first carries the eyes and ocelli, the 

 second the antennae, the third has no appendages but bears the labrum, 

 the fourth carries the mandibles, the fifth the maxillae, and the sixth the 

 lower lip. 



Vision of Caterpillars and Adult Insects.f — Prof. F. Plateau con- 

 tinues his researches on the powers of vision by an investigation of cater- 

 pillars and of the frontal ocelli of adult insects. 



(1) He made a series of experiments and observations on the cater- 

 pillars of fifteen species of Lepidoptera, and obtained the following 

 results : — (a) The eyes of caterpillars have a more important role than 

 that of simply distinguishing between light and darkness. They really 

 see, though badly, (b) The distance of distinct vision is short, and 

 usually about a centimetre, (c) At greater distances caterpillars can 

 perceive large masses, but do not discern their nature, (rf) They only 

 perceive the movements of bodies within the limits of distinct vision, 

 (e) Tactile hairs present on the anterior segments of many forms are 

 of much sensory importance. (/) The antennge are much used in 

 testing the path and surrounding objects. 



(2) In the next chapter Prof. Plateau discusses the function of the 

 frontal ocelli of adult insects. He gives an historical summary of past 

 researches, describes the manifold conditions of his own observations 

 and experiments, submits tabulated results of his investigations of 



* See this Journal, 18S7, p. 379. 



t Bull. Acad. R. Soi. Belg., xv. (1888) pp. 28-91. 



