ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



in the latter case there is in the main axis a hollow, clapper-like, median 

 portion composed of hollow, but peculiarly chambered spines ; the spines- 

 are disposed singly or in pairs in cruciate arrangement around the main 

 axis." There is only one main opening in the central capsule ; parapylea 

 are absent. It is the presence of a phaeodium-like pigment-mass that 

 points to affinity with the Tripylea. The family is represented by the 

 genus Atlanticella, with three species. There seem to be near affinities 

 with the Medusettidaj. The habitat of the Atlanticellidse is especially 

 in the deeper regions of the Atlantic ; they appear to be absent in the 

 cold northern regions. 



Xenophyophorse.* — F. E. Schulze discusses a peculiar group of 

 Rhizopods from abyssal regions, e. g. Psammetta erythrocytomorpha,. 

 Psammina globigerina, Stannoma dendroides. They are not sponges, as 

 has been suggested, but represent a group of Protozoa within the 

 Rhizopod class, and near Foraminifera. The term Xenophyophorae . 

 refers to the characteristic utilisation of extrinsic foreign bodies such as 

 the spicules of Tetraxonid sponges. 



Dimorphism of English Nummulites.f — J. J. Lister finds, from an 

 examination of the Nummulites of the Eocene beds of the Isle of Wight 

 and Hampshire, proof of the existence of alternating members of 

 " a pair " of forms in the life-history of a species. The two modes of 

 reproduction come into marked contrast, the asexually produced megalo- 

 spheres being approximately proportional in size to the protoplasmic 

 volume of the parent while the microsphere probably arising as a zygote 

 is uniformly small throughout. In several of the species examined, as 

 the microspheric member of the cycle preponderates in the life-history,, 

 the megalospheric member decreases, not only in proportion to the size 

 of the microspheric form, but in proportion to the megalospheric 

 members of other species in which the two forms attain approximately 

 equal sizes. 



Barium Sulphate in a Rhizopod.| — F. E. Schulze and Hans Thier- 

 felder note that in a peculiar abyssal Rhizopod, Xenophyophora, the 

 cytoplasm includes minute refractive granules which consist of barium 

 sulphate with traces of calcium sulphate. The only other known case of 

 barium in organisms is in some marine plants (" Forchhammer "). 



Life-History of Hypotrichous Infusoria. § — L. L. Woodruff has. 

 investigated this in Oxytricha, Pleurotricha, and Gastrostyla. In one 

 culture as many as 860 generations were attained. All the cultures gave 

 incontestable proof that the forms studied pass through cyclical periods 

 of greater and less general vitality as measured by the rate of division. 

 The periods of depression lead to death if the culture is subjected con- 

 tinuously to the same environment. Minor fluctuations, termed rhythms, 

 occur in the division rate ; they are periodic rises and falls due to some 



* Wiss. Ergebn. Deutsch. Tilfsee Exped. Valdivia, xi. (1905) pp. 1-55 (8 pis.) . 

 See also Zool. Zentralbl., xiii. (1906) pp. 238-42. 



t Proc. Roy. Soc, Series B, lxxvi. (1905) pp. 298-319 (3 pis.). 



\ SB. Ges. Nat. Freunde Berlin, 1905, pp. 2-4. 



§ Joum. Exper. Zool., ii. (1905) pp 585-632 (3 pis.). 



