ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 787 



egg, the apertures of these two series of structures would exactly 

 correspond. 



In the silkworm the stigmata are absent on the last three seg- 

 ments, and there are three pairs of Malpighian tubes. 



There are three pairs of ectodermic pits, corresponding to the 

 three buccal segments ; and although their position differs from tbat 

 of the stigmata, Grassi considers these salivary and spinning glands 

 to be homologous with trachea). All the above-mentioned organs 

 are, whilst in the egg, filled with the amniotic liquid, and the author 

 considers that they are all excretory organs during development 

 within the egg. 



Palmen and Gegenbaur have suggested that the trachea) were 

 originally excretory organs, and only secondarily became respiratory. 

 If it could be shown that the antennary glands and other presumably 

 excretory organs in Crustacea, and the nephridia in worms, are all ecto- 

 dermic in origin, there would be an homology between all these organs. 



e. Circulatory system. — The hypothesis of Biitschli that the vessels 

 are the remnants of the segmentation cavity may well be true, if the 

 space between ectoderm and endoderm, and the mesoderm (due to 

 the withdrawal of the yolk), and from which the dorsal vessel is 

 formed, is to be considered as a segmentation cavity. 



/. Appendages. — The first pair of buccal appendages, which almost 

 immediately disappears, may perhaps be the homologue of'the second 

 pair of crustacean antennas. 



Tho disappearance of certain appendages proves that the larva) of 

 the ancestors of the bee lived a free life, and resembled the genus 

 Campodea. This supports the theory that the latter are to be con- 

 sidered as proto-insects. 



Luminous Organs of the Mexican Cucuyos.* — Herr C. Heinc- 

 mann communicates a detailed account of his researches on tho 

 anatomy and physiology of the luminous organs of certain Mexican 

 Pyrophori, or Cucuyos. 



a. Macroscopic. — The organs in question consist (1) of two elliptical 

 patches on the upper surface of the prothorax, and (2) of a ventral 

 organ on the first ventral ring of the abdomen. Their more exact 

 position is carefully defined. They arc known to be special differen- 

 tiations of the dermal matrix — the so-called hypedermis. Even with 

 the naked eye, two layers are distinguishable, an external luminous 

 stratum, wax-like in the daytime, and a non-luminous, white, lower 

 layer. 



b. The respiratory system. — After describing tho disposition of the 

 tracheae, Herr Heincmann seeks to establish from his observations tho 

 following statements: — (1) The inspiration occurs passively, but the 

 exspiration is effected by the contraction of the muscles connecting 

 the rings of the body ; (2) the respiratory movements of the beetles 

 are restricted to the abdomen ; (3) the movements are continued as 

 usual, even after the removal of the head and prothorax, so that the 

 innervating centre cannot be exclusively sought in the oesophageal or 

 in the prothoracic ganglion. 



* Arch, f. Mikr. Anat., xxvii. (1886) pp. 290-382. 



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