ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 275 



and found them specially favourable objects for the study of the central 

 corpuscles, which here occupy a remarkable position. At the beginning 

 of the mitosis two central corpuscles with their rays are present, and 

 lie at some little distance from the poles of the nucleus. Before any 

 change takes place in the nucleus, they travel in opposite directions 

 outwards to the cell-periphery. The cytoplasmic rays radiate out from 

 ths central corpuscles, but these have no connection with the threads of 

 the nuclear spindle, which end free. The later stages of the mitosis 

 were not followed, but the authors compare their observations with those 

 of various authors (Hirase, Webber, Ikeno), on the sex-cells of Cycads, 

 where again central corpuscles (blepharoplasts) occur, which are not 

 related to the nuclear spindle. 



y. Protracheata. 



Spermatogenesis of Peripatus balfouri.* — Dr. T. H. Montgomery 

 finds that there is much similarity between the spermatogenesis of 

 Peripatus and that of Insects, and that the synaptic stage is shown in 

 Peripatus with exceptional clearness. As in Pentatoma, the synapsis is 

 a part of the anaphase of the spermatogonic mitosis, and is followed 

 by a complete rest stage. In connection with his observations on the 

 chromosomes, the author makes some remarks on the use of the term 

 chromosome. He regards the nuclear network as composed of linin and 

 chromatin, while there are in addition achromatic threads which may 

 connect the chromatin granules with the nuclear membrane, and are pro- 

 visionally called " secondary linin fibrils " by the author. When the 

 chromatin granules are densely concentrated on the linin threads, a 

 " chromosome " is formed, but the linin connections between the granules 

 persist, and form the matrix of each chromosome. In Peripatus the 

 author finds reason to believe that in spite of the changes undergone by 

 the chromosomes, a continuous linin spirem persists continuously from 

 the prophase of the last spermatogonic division, through the rest stage 

 of the spermatocytes, up to the monaster of the first maturation division. 

 He therefore regards linin spirem and chromatin as constituting together 

 a single nuclear element, whose component parts — the chromosomes — 

 are continuous from generation to generation of the cells. He believes 

 that the presence of a persistent and continuous linin spirem furnishes 

 an explanation of some hitherto obscure cytological phenomena. 



5. Arachnida. 



Palaeophonus hunteri sp. n.f — R. I. Pocock has examined this form, 

 the Scottish Silurian scorpion of Mr. Peach, which proves to be distinct 

 from the hitherto described Swedish Upper Silurian scorpion. From 

 the position of the specimen it is possible to study the under surface, 

 and this leads to the conclusion that Palaeophonus is to be regarded as 

 occupying an intermediate position between Limulus and the Eurypterids 

 on the one hand, and recent scorpions on the other. Indeed, P. hunteri 

 affords additional proof of the descent of scorpions from marine Limuloid 

 ancestors. The author doubts the existence of stigmata, and believes 

 that Palaeophonus lived in the sea, breathing partly by means of the 



» Zool. Jahrb., xiv. (1900) pp. 277-368 (7 pis.). 



t Quart. Journ. Micr. Sci., xliv. (1901) pp. 291-311 (1 pi. and 3 figs.). 



