450 SUMMARY OF CURRENT RESEARCHES RELATING TO 



as a specific structure throughout until it disintegrates in the head of the 

 ripening spermatozoon. 



Diaposematism.* — Guy A. K. Marshall discusses reciprocal mimicry 

 and some limitations of the Miillerian hypothesis of mimicry. He points 

 out the difficulty of accepting the idea of a mutual simultaneous mimicry 

 between two unpalatable species, such as is postulated by the hypothesis 

 of " diaposematism." It is suggested that an initial inequality in the 

 individual numbers of the two distasteful species is an essential condition 

 for the production of Miillerian mimicry, and that in such circumstances 

 the mimetic approach would always be in one direction only, namely, 

 from the rarer species towards the more abundant. Any initial varia- 

 tion from the latter towards the former must be disadvantageous. 



The various cases which have been cited in evidence of diaposematism 

 or reciprocal mimicry are critically examined, and it is argued that the 

 facts can be more satisfactorily interpreted on lines which do not involve 

 the assumption of a mutual interchange of characters between mimic 

 and model. Miiller's principle is important, but it has definite limitations, 

 and the attempt to explain all cases of mimicry among butterflies on the 

 Miillerian theory is contested. The wide significance of Bates's principle 

 has not been adequately appreciated. Indeed the theory of Bates will 

 explain many cases of mimicry between unpalatable species which have 

 been previously considered as purely Miillerian in character. 



Accessory Chromosome in Anasa tristis.f — ■ E. B. Wilson, in 

 opposition to the criticisms of Foot and Strobell, who could find no 

 accessory chromosome in Anasa tristis, confirms his previous conclusion 

 that the number of chromosomes in the spermatogonia is 21, in the eggs 

 22 ; and that the accessory chromosome in the second maturation 

 division passes undivided to one pole, so that half of the spermatozoa 

 have 10 chromosomes, and half have 11 chromosomes. 



Cutaneous Glands of Wasps 4 — L. Bordas finds in various species 

 of Vespa, groups of unicellular glands on the anterior margin of the two 

 last abdominal sternites. Each gland is a large spherical cell, with a 

 delicate canal passing to the exterior, and often uniting with several 

 others. 



Cave Beetles. § — Pi. Jeannel describes a large collection (31 species) 

 of beetles from Pyrenean and other caves. He deals with several new 

 forms — e.g. Speodketus g.n. and Speonomus g.n., including species pre- 

 viously referred to Bathyscia. 



Development of the Alimentary Canal during Metamorphosis. || 

 P. Deegener follows up his previous account (190-1) of the develop- 

 ment of the alimentary canal in Cybister roeselii, with a careful description 

 of all the changes undergone in Malacosoma castrensis during metamor- 

 phosis. 



* Trans. Entomol. Soc, Loudon, 1908, pp. 93-142. 



f Science, xxv. (1907) pp. 191-3. 



j Bull. Soc. Zool. France, xxxiii. (1908) pp. 59-64 (3 figs.). 



§ Arch. Zool. Exper., viii. (1908) pp. 267-326 (3 pis.). 



|| Zool. Jahrb., xxvi. (190S) pp. 45-182 (5 pis. and 1 fig.). 



