ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 75 



peripheral ends, or by small isolated crystals. According as the 

 skeletal pieces are formed by solid masses, or by numerous lamellae, 

 with intermediate spaces, we have the Madreporaria aporosa, or 

 porifera. The development of the skeleton has only been worked 

 out in Astroides calycularis, and there the ectoderm of the pedal disk 

 gives rise to a thin calcareous plate — the sclerobase of the future 

 polypary. The crystalline corpuscles, which make it up, appear to be 

 secreted by the ectodermal cells, and they soon fuse with one another 

 and take on a polyhedral form. 



The porcellanous membranes, which are found in such forms as 

 Calliadis, probably belong to the skeletal series, and may be regarded 

 as the analogue of the JSrst rudiment of the skeleton. The horny 

 skeletons are either connected secretions of an epithelium, or invest- 

 ments, varying in thickness, of the calcareous corpuscles. The former, 

 when simplest, are thin lamellae which present a striated structure, 

 and are developed from the ectoderm of the foot-disk (some Actiniae). 

 In the Oornularidas they are better developed, and form a more or less 

 firm test, into which the whole polyp can be retracted. They are 

 made up of thin lamellae, which are not separated by any interspaces, 

 and are only with difficulty separated from one another. In the 

 Antipathidse and Gorgonidae — e. g. Gerardia — the ectoderm secretes a 

 horny lamella, which differs a good deal in the different families and 

 genera, as to the extent to which inorganic substances enter into its 

 composition. The study of Gorgonia shows that the simple polyps 

 first secrete at their distal end a thin horny lamella. The growth of 

 the axial skeleton is pari passu with the formation of polyps, till at 

 last we have a colony of a number of separate animals, which appear 

 to invest the axial skeleton, although this last is a product of the 

 primitive ectoderm. The axis of the Pennatulidse presents a consider- 

 able resemblance to that of the Gorgonidae, and in them, too, there is 

 an axial epithelium. 



The horny sheaths of the spicules must be regarded as products of 

 the cells, and not as hardenings of the intermediate substance ; this is 

 demonstrated by their relations, both in early and late life, to the 

 protoplasm of the cells. These sheaths often secondarily fuse with 

 one another and then form pretty strong skeletal parts, as in the axes 

 of Sclerogorgia, &c. 



Protozoa. 



Suctociliata, a New Group of Infusoria, intermediate between 

 the Ciliata and the Acinetina.* — Well-marked characters separate 

 the ciliated Infusoria from the Acinetina ; and up to recently no 

 intermediate form has been indicated as forming the passage between 

 the two groups. In the Bay of Naples, however, Dr. C. de Meresch- 

 kowsky met with an intermediate form, presenting at the same time 

 the cilia of the ciliated Infusoria and the suckers of the Acinetina. 



At first glance it might be taken for a Halterine, to which it 

 presents some resemblances. In size it does not exceed a small 

 Halteria; its body, which is rounded and somewhat pyi'iform, ter- 



* Comptes Rendus, xcv. (1882) pp. 1232-5. 



