5 8o SCIENCE PROGRESS 



Male" {Biol. Bull., vol. xxxvii, Sept. 1919) ; and Whitney, " The Ineffective- 

 ness of Oxygen as a Factor in causing Male Production in Hydatina senta " 

 (Joum. Exp. Zool., vol. xxviii, July 1919)- 



Interesting results have been recorded by Gould in " Studies 

 on Sex in the Hermaphrodite Mollusc Crepidula plana : 

 III, Transference of the Male-producing Stimulus through Sea- 

 water " {Joum. Exp. Zool., vol. xxix, Aug. 1919). As is known, 

 this animal exhibits a male phase, a transitional phase, and a 

 female phase, during its life-history. The observations tend to 

 show that well-grown specimens produce an unstable substance, 

 diffusible in sea-water, that acts as a stimulus to young or smaller 

 individuals, causing them to develop into full males. In the 

 absence of this stimulus the male phase is suppressed. The 

 action is apparently specific, for large C. fornicata do not seem 

 to be able to call forth this response in a small C. plana. 



Other papers include : 



Copeland, " Locomotion in Two Species of the Gasteropod Genus Alectrion, 

 with Observations on the Behaviour of Pedal Cilia " (Biol. Bull., vol. xxxvii, 

 Aug. 1 91 9) ; and Guthrie, " Cleavage and Mesenchyme Formation in Toxo- 

 pneustes variegatus " (Biol. Bull., vol. xxxvii, Sept. 1919). 



Bridges has added another to the already numerous papers 

 on Drosophila in " Specific Modifiers of Eosin Eye-colour in 

 Drosophila melanogaster " (Joum. Exp. Zool., vol. xxviii, 

 July 1 91 9). In this it is claimed that eight mutant genes have 

 been demonstrated which, while by themselves producing no 

 effect, are yet capable of modifying the eye-colour in the sex- 

 linked mutant " eosin." These modifiers can alter the eosin 

 colour from shades darker than eosin on the one hand, to a pure 

 white on the other. It is suggested that " The main signifi- 

 cance of the facts presented is in their bearing on questions of 

 the method by which selection attains its results." The chro- 

 mosomes of insects, ever favourite objects of investigation, have 

 been treated by Goldsmith, in " A Comparative Study of the 

 Chromosomes of the Tiger Beetles (Cicindelida?) (Joum. Morph., 

 vol. xxxii, Sept. 191 9), and by Nakahara in " A Study of the 

 Chromosomes in the Spermatogenesis of the Stonefly, Perla 

 immarginata, Say, with Special Reference to the Question of 

 Synapsis " (ibid., Sept. 191 9). The former shows that, according 

 to previous workers, three types of chromosome behaviour 

 may be recognised in beetles, one in which hetero-chromosomes 

 are present, one in which a bipartite deeply staining body is 

 found, and lastly one in which a single odd chromosome makes 

 its appearance. It is noted that the germ cells of the female 

 appear to contain about twice as much chromatin as those of 

 the male. The various division stages are fully described and 



