ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 205 



time the principal axis becomes more strongly curved, and the cell 

 shorter and broader. This change of form depends exclusively on 

 the contraction of the inner fibres, the other parts of the cell remain- 

 ing quite passive. The movements of the cells soon begin to slacken, 

 become irregular and feeble, finally cease, and the cell bursts. Its 

 protoplasm soon perishes, but the fibres resist for a longer time the 

 action of the water, and even exhibit a trace of contractility like 

 dying cilia. 



Numerous observations have convinced Mr. Geddes that these 

 cells are in reality parasites. Other species of Planarians possess 

 nothing like them. The delicacy of their protoplasm distinguishes 

 them from the true tissue of the Convoluta. Moreover, they do not 

 form tissue, and have no definite disposition. Eegarded as parasites, 

 their structure, apparently so abnormal, is readily derived from the 

 type of ordinary Infusoria by the suj)pression of the cilia (which 

 would not be available for locomotion among the cells of the meso- 

 derm) and the differentiation of the contractile vesicle. 



This differentiation is certainly very remarkable from every point 

 of view when we consider the relatively enormous size of the vacuole, 

 the development of the contractile fibres which limit it, or the rapidity 

 of their contraction. 



The author proposes to call this Infusorian Pulsatella convolutoe, 

 and as it is so distinct from either Suctoria, Ciliata, or Flagellata, to 

 create for it a fourth sub-class Pulsatoria. 



Skeleton of the Radiolaria.* — Professor Biitschli deals especially 

 with the Cyrtida, having had the advantage of studying a number of 

 fossil specimens from Barbadoes. He commences with a study of 

 Gcelothamnus (?) davidoffii n. sp., a Phoeodarian in which the skeleton 

 is as much as 1^ cm. in diameter. Examined with the naked eye, 

 it is seen to be a (marine) organism, stellate in form, with sixteen 

 relatively long rays, which appear to arise from a common centre. 

 These rays are skeletal parts, and are, with the centre, imbedded in 

 a common gelatinous mass. Belonging to Haeckel's family Coelo- 

 dendrida, its exact generic position must still remain a matter for 

 discussion. The central portion is formed of two separate valves, 

 which resemble one another in their structure, though not in their 

 form. The details of their characters and of their connection with 

 the rays is given. 



The structure and relations of the Acanthodesmida, Zygocyrtida, 

 and Cyrtida (Cricoidea : Biitschli) are then dealt with in detail ; and 

 the author concludes by pointing out that he cannot regard as natural 

 Haeckel's division of the Cyrtida into Mono-, Di-, and Sticho-cyrtida. 

 He can only distinguish two separate phyla, but he is careful to point 

 out that our knowledge of these forms is at present very slight. 



Recent Researches on the Heliozoa. — L. Maggi f has observed on 

 a Spirogyra a form belonging to Cienkowski's genus Nuclearia, and, 



* Zeitschr. f. wiss. Zool., xxxvi. (1881) pp. 485-540 (3 pis.), 

 t Rendic. R. Istit. Lomb., xiii. (1880) fasc. 20. Of. Zool. Jahresber. Neapel 

 for 1880, i. pp. 154-5. 



