ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 573 



was able to detect within the circular canal, on the anal side, a sharply 

 defined orgau, which looked very like a ganglion. The gonads are 

 always products of the parenchymatous tissue, but the size of the ovary 

 and ova varies considerably ; in Flustra carbasea the spermatozoa-spheres 

 form a compact cell-mass. In Crista the formation of the generative cells 

 appears to go on exclusively in the brood-capsules. The intertentacular 

 organ of Alcyonidium mytili is not present in all functional individuals of 

 the colony ; it lies beneath the tentacular sheath, has an epithelial invest- 

 ment, and is fused for a large part of its course with the adjacent tentacles 

 of either side. 



y. Brachiopoda. 



Anatomy of Brachiopoda Articulata.* — Dr. L. Joubin, who has already 

 investigated the inarticulate Brachiopoda, has extended his studies to Tere- 

 bratulina, Argtope, &c. Longitudinal sections of young forms show that the 

 peduncle is a sac which is entirely closed, and is applied against the hind 

 wall of the mantle, an arrangement, therefore, analogous to what obtains in 

 Discina. By the aid of figures the author describes the minute structure 

 of the stalk and of its appendages. These latter can only be made out in 

 young forms, as they soon become incrusted. There are a varying number 

 of small yellowish hairs, which terminate by a kind of sucker. The hairs 

 are hollow, and the walls are formed of a series of zones arranged concen- 

 trically round a lumen. Each hair is fixed in the thick layer of cartilaginous 

 tissue which forms the end of the peduncle. In function they appear to be 

 comparable to the byssus threads of lamellibranch molluscs, but in their 

 mode of development, and their morphological relations, they are altogether 

 different. 



Caecal Processes of Shells of Brachiopoda.j — Prof. W. J. Sollas 

 adduces evidence that the so-called caecal processes of the shells of 

 Brachiopods are sense-organs ; they are obviously composed of epithelial 

 cells, and in their centre they show traces of an axial fibre, which can be 

 seen to be continuous with the nerve-cells of the mantle. At the outer end 

 of the tubule there is a single large finely granular cell, with a large oval 

 nucleus and spherical nucleolus, and there may be, in addition to it, a 

 number of other nuclei. The inner end of the terminal cell appears to be 

 prolonged into a fibril, which can sometimes be traced into continuity with 

 both the nucleus and the axial fibre. The ca3cal tubes of Waldheimia 

 cranium are, therefore, epidermal outgrowths with a large terminal granular 

 cell, which is continued proximally into a nerve-fibril and is covered distally 

 by a transparent chitinous layer, separating it from all external influences 

 likely to serve as stimuli except that of light ; that, however, the ctecal 

 process is an organ for the perception of light cannot yet be taken as 

 proved, owing, especially, to the absence of anything like pigment in the 

 terminal cells. Specimens better prepared may perhaps add to our 

 information on this point. 



Arthropoda. 



Relations of Groups of Arthropoda.| — Prof, C. Claus states that the 

 " essential points " on which he insists are — 



^ (1) He independently supported, eleven years ago, the phylogenetic 

 origin of Scorpions and other Arachnoids from the Gigantostraca. 



* Bull. Soc. Zool. France, xii. (1837) pp. 119-26 (1 pi.), 

 t Scientif. Proc. R. Dublin Soc, v. (1887) pp. 318-20 (1 fig.). 



X Arbeit. Zool.-Zoot. Inst. Wieu, vii. Ct. Ann. uud Mag. Nat. Hist, xix. (1887) 

 p. 306. ■ 



