ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 395 



Incertae Sedis. 



Early Tertiary Cheilostome Bryozoa.* — Ferdinand Canu and Ray 

 S. Bassler give a synopsis of American Early Tertiary Cheilostome 

 Bryozoa. " In the Bryozoa, as in other living beings, the form is only 

 the resnlt of a function ; therefore in the study of the morphological 

 variations of the organs we now substitute that of their physiologic 

 function. Our studies are therefore always directed toward the discovery 

 of functions which modify the skeletal form." 



•' All the species which have the same larval form have the same 

 lineage and belong necessarily to the same family ; therefore the family 

 is characterized by the larval system. The ovicell in which the larva 

 develops is necessarily in rapport with it, and a knowledge of its 

 structure gives the essential characters for readily interpreting the 

 physiological purpose of the morphological and skeletal variations." We 

 have given the authors' words, but we do not clearly follow them. 



" A really natural genus differs from another genus only in possessing 

 a different function and in the different form of any skeletal part. The 

 essential functions common to all Bryozoa without exception are : — 



" 1. Passage of eggs and escape of the larvae ( = rapport of the 

 operculum and the ovicell). 



"2. Hydrostatic system and extrusion of the polypide ( = form of 

 the aperture and rapport of the operculum with the compensatrix). 



" ?). Calcification and chitinisation ( = nature of the skeleton and of 

 the frontal considered as immediate deposits of the endocyst." 



" The function of the avicularia and of the onychocellaria is not 

 known, but it cannot be common to all Bryozoa, because many species 

 are deprived of these structures." They cannot therefore furnish good 

 generic characters, but they may be utiHzed in cases where they seem 

 mdispensable to the life of the zoarium. The authors describe many new 

 genera and species. 



Development of Cephalodiscus.t — J. D. F. Gilchrist gives an 

 account of the development of the Cape Gephalodiscus (0. ffilchristi, 

 Ridewood). He notes some facts with regard to the formation 

 of yolk-granules, the presence of yolk-nuclei, and the character 

 of nucleus and nucleolus. The segmentation is holoblastic, equal, 

 or markedly unequal, and apparently indeterminate. A blastula 

 stage occurs. The blastula becomes solid by proliferation of cells 

 at one end ; there is no invagination at this stage. The point of 

 proliferation marks the posterior end, and the anterior end is dis- 

 tinguished by the elongation of its cells. All the outer cells become 

 elongate and assume the character of columnar cells full of yolk. As 

 these increase in number a small posterior invagination appears. The 

 cellular character of the yolk columns disappears ; the yolk granules 

 are used up, and an ectoderm consisting of many nuclei in a proto- 

 plasmic network with a basement of membrane is formed. Excretory 



* U.S. Nat. :\Iuseum, Bull. No. 96 (1917) pp. 1-87 (6 pis.), 

 t Quart. Journ. Micr. Sci., ii. (1917) pp. 189-211 (3 pis.). 



2 D 2 



