502 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



base of the legs. Mr. Patten thinks it is clear that the eyes are serially 

 homologous with these thoracic sense-organs. The latter contain a 

 cavity, shaped like the bowl and stalk of a goblet, lined with striated 

 cuticle similar to that found at an early stage over the eyes of Acilius. 

 The ventral cord and brain of Arthropods are at first composed entirely of 

 minute sense-organs, which in scorpions have the same structure as the 

 segmental ones at the base of the legs. Further details are promised. 



a. Insecta. 



Formation and Fate of Polar Globules in Eggs of Insects.*— 

 Dr. H. Henking has examined the early stages of development in the. 

 eggs of various Insects. 



In the egg of Pyrrhocoris apterus the first polar globule appears three 

 or four hours after deposition ; it lies in a shallow depression of the 

 marginal zone of protoplasm ; below it may be seen the second globule 

 in a more or less advanced stage. When the first embryonic cells begin 

 to be formed within the egg, the globules come to be placed freely in a 

 cavity which is altogether surrounded by the marginal protoplasm ; they 

 have not yet, however, acquired their definite position. In eggs about 

 twenty hours old the globules lie outside the protoplasm on the surface 

 of the ventral yolk-material. The author's opportunities of observation 

 have not as yet enabled him to definitely settle the fate of these bodies, 

 but he is satisfied that the globules are again taken up by the egg. In 

 the case of various Lepidoptera, Diptera, and Hymenoptera, Dr. Henking 

 has not been able to observe the expulsion of the polar globules. In 

 Tenehrio molitor one is certainly expelled, and the same is the case in 

 Lampyris splendidula. 



Vision of Insects. f — -Dr. F. Dahl, who believes that Insects can dis- 

 tinguish form, traverses certain conclusions of Prof. Plateau, for which 

 he does not believe there are physiological grounds. He relates an 

 account of an experiment which he made with a bee {Hylseus morio), 

 whose enemy is the spider Aitus arcuatus ; thinking that the olfactoiy 

 sense might give the insect warning, he killed a spider, and smeared a 

 paper-sphere with its blood, but of this the bee was not at all afraid. 

 The male of the dipterous Dolichopus plumipes has a beautiful and 

 regular pinnation of the first tarsal joint of the middle leg ; this 

 apparatus cannot be of use during copulation. When the insects were 

 pairing it was observed that the male hovered over the female in such a 

 way as to bring its middle tarsi close to the eyes of the female. 



Dr. D. Sharp \ devoted a large part of his Presidential Address to 

 the Entomological Society of London to the subject of the vision of 

 Insects. He thinks we may fairly conclude that it is quite uncertain 

 what insects do see, or whether they see at all, if we use the word seeing 

 in association with our own plane-picture seeing. He lays stress on 

 the point that, certain central structures in connection with the verte- 

 brate sense of sight not being present in insects, other structures to 

 compensate for their absence may be expected to occur in more direct 

 connection with the eye. If so, it becomes highly probable that the 

 functions of the insect-eyes are not only dissimilar from ours, but are 



* Nachr. K. Gesell. Gottingen, 1888 (1889) pp. 444-9. 



t Zool. Anzeij-;., xii. (1889) pp. 243-7. 



X Trans. Eutoinol. Soc. Lond., 1888 (1889) pp. xlviii.-lxix. 



