ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 291 



and finally sombre red. Extracts of the gland in alcohol, ether, or 

 chloroform give the purple colour on exposure to light, a phenomenon 

 probably associated with the oxidation of the photochemical substances. 

 He finds no contradiction in the results reached by Dubois, whose work 

 deals with antecedent stages, or in his theory that the secretion which 

 becomes purple on exposure to light is the outcome of an interaction 

 between a ferment (purpurase) and another substance (purpurin). 

 Letellier did not go so far back, his observations dealt with the already 

 formed secretion. 



Nematocysts of Nudibranchs.* — 0. C. Glaser discusses the inter- 

 esting question whether the cnidoblasts observed in Eolididae are really 

 parts " of the organic make-up " of these molluscs, or have been in- 

 corporated from the hydroids among which the nudibranchs live. Hio 

 results are inconclusive, i.e. his facts can be explained on the assumption 

 that the nematocysts do not really belong to the molluscs. " If this 

 hypothesis is true, we are dealing with a most remarkable adaptation, 

 in which weapons are taken from one animal and actually used by 

 another." At all events, " there are good reasons why the origin of the 

 nematocysts of the Eolidida3 should be carefully studied." " Such study 

 may show that they are not part of the organic make-up of the animals 

 possessing them." 



Tracheopulmonate Gastropods.f — G. Glamann has studied some of 

 the remarkable Australasian Janellidse, in which there are only two 

 tentacles, and in which there is " a tufted lung " (Biischellunge), with 

 diverticula and respiratory tubules surrounding the pulmonary cavity 

 and allowing of gaseous exchange between the tubules and the hgemo- 

 lymph in the large dorsal sinus embracing the lung. 



The author gives a detailed account of Aneitea graffei, and Aneitella 

 virgata ; a diagnosis of the Janellidre, a key to the species of Aneitea, 

 and a re-statement of the characters of the four genera — Janella, 

 Triboniopliorus, Aneitea, and Aneitella. 



5. Liamellibranchiata. 



Origin of Pearls in Mytilus gallo-provincialis.J — R- Dubois notes 

 that his observation that the pearls of Mytilus edulis are due to a para- 

 sitic fluke was independent of the work of Gardner (1871) and of Lyster 

 Jameson. He has also found in M . gallo-provincialis, which differs in 

 habitat and environmental conditions, another species of fluke also 

 causing pearls. In pearls from Anodonta cygncea, he found no trace of 

 parasites, and thinks that the theory of the parasitic origin of pearls 

 must not be hastily generalised. 



ArthropcJda. 

 o. Tnsecta. 



Evolution of Colour-Patterns in Lepitloptera.§— A. G. Mayer has 

 inquired into the effects of natural selection and race-tendency upon the 



* Johns Hopkins Univ. Giro., xxii. (1903) pp. 22-4. 

 t Zoo]. Jahrb., xvii. (1903) pp. 679-762 (6 pis. ami 9 figs.). 

 X Coruptes Rendus, cxxxvi. (1903) pp. 17S-9. 



§ PuUiealions of Museum of Brooklyn Inst. Sci. Bulletin, i. No. 2 (1902) 

 pp. 31-86 (2 pis.). 



