ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 435 



lies between the upper and lower walls of tlie diverticulum ; at its 

 hinder end, or at the base of the follicle, there are a number of 

 specially developed epithelial cells, by the secretion of which the 

 teeth and the basal membrane are formed ; the formative cells or 

 " odontoblasts " are of two forms and sizes ; we either find that there 

 is a small number of large cells with large nuclei and clear proto- 

 plasm, which unite into an almost circular closed groove, as in 

 Pulmonates and Opisthobranchs, or there are a large number of small 

 odontoblasts, which are only occasionally to be distinguished from 

 the surrounding epithelial cells ; these unite to form an almost 

 hemispherical prominence in Prosobranchs, Placophora, Heteropoda, 

 and Cephalopoda. 



In the Pulmonates and Opisthobranchs, which are distinguished 

 by the uniformity of their teeth, four or five cells take part in forming 

 a tooth, while the subjacent portion of the basal membrane is formed 

 by a single cell, the size of which is in direct relation to the strength 

 of the basal membrane. The odontoblasts are not replaced by new 

 cells after the formation of one tooth, but the group of cells forms all 

 the teeth of one longitudinal row. In the other Mollusca the cushion 

 of odontoblasts breaks up into as many separate divisions as there are 

 teeth in one transverse row of the radula ; the striated basal membrane 

 is formed by the lower portions of the epithelial cushion, and the 

 ends of the matrix-cells break up into parallel fibres, which elongate 

 and lie side by side. The forward movement of the radula is to be 

 regarded as a phenomenon of growth. 



New 'Challenger' Cephalopoda.* — Mr. W. E. Hoyle gives 

 diagnoses of new species of Cephalopoda collected during the cruise 

 of the ' Challenger.' In this first part the Octopoda are dealt with, 

 comprising eleven new species of Octopus (with one new variety) ; 

 two of Eledone ; two belonging to a new genus, Jajpetella ; three to 

 Cirroteuthis ; and one to a new genus, Ampliitretus. 



Intercellular Spaces of Epithelium, and their significance in 

 Pulmonate MoUusca.f — Herr A. Nalepa, on examination of the land 

 pulmonates of Austria, finds that fresh tegumentary epithelium, 

 which is best taken from the margins of the foot of small Helicidge, 

 consists of irregular, many-sided, cylindrical cells, the height of 

 which varies considerably ; the separate cells are not closely packed, 

 but have a delicate space between them ; this may at some points 

 widen out, and so give rise to the so-called dermal pores. The 

 spaces traverse delicate bridges of substance which connect the cells 

 with one another. The author is of opinion that these are true 

 intercellular spaces, which are connected on the one hand with blood- 

 spaces, and on the other with the surrounding medium ; and he thinks 

 that his method of investigation excludes any other explanation. He 

 regards the pores not only as means by which water may enter the 

 hsemo-lymph system, but as having also a relation to the processes of 

 excretion. 



* Ann. and Mag. Nat. Hist., xv. (1885) pp. 222-36. 



t SB. K. K. Akad. Wiss. Wien, Ixxxviii. (1884) pp. 1180-9 (1 pi.). 



2 P 2 



