ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
297 
investigation is to show the extraordinary polymorphism of these ele- 
ments and the existence of transitions between the different forms. 
What have been called “ ramified,” “ vesicular,” “ plasmatic,” “ stellate,” 
“ multipolar ” cells, and by many other names according to their forms, 
are all reducible to one type. 
Tylodinidse.* — Dr. G. Mazzarelli describes the structure of Tylo- 
dinella Irinchesii g. et sp. n., for which, along with the two known species 
of Tylodina Raf., he proposes to establish a new Tectibranch family 
Tylodinidjs. Of this a full diagnosis is given. After discussing the 
affinities, the author agrees with Pelseneer that the type represents the 
stock from which the Pleurobranchidse are derived. 
Parasitic Prosobranchs.l — Prof. W. Kukenthal describes six species, 
two new, which he found associated with Echinoderms at Ternate. He 
discusses their structural peculiarities in relation to their mode of life. 
They belong to two distinct series, the one having its nearest relatives 
in the Eulimidee, the other in Capulus and Hipponyx. An extreme is re- 
presented by Stilifer , whose peculiarities, such as the false mantle, are 
made more intelligible by a study of Mucronalia eburnea and other 
species. 
Freshwater and Terrestrial Gastropoda from Halmahera, &c.J — 
Dr. W. Kobelt gives an account of Kiikenthal’s collection from Hal- 
mahera, Batjan, Celebes, and North Borneo, and establishes numerous 
new species. 
Opisthobranchs of Ternate.§ — Prof. R. Bergh describes Kukentlial’s 
collection, including Kentrodoris maculosa , Asteronoius cespitosus, Phyl- 
lidia varicosa, and Doridium alboventrale sp. n. 
Species of Vaginula.jl — Prof. H. Simroth describes three of these 
slugs collected by Kukenthal, — Vaginula Strubelli from Java, V. djilolo- 
ensis sp. n. from Halmahera, and V. borneensis sp. n. from Borneo. 
Degenerative and Regenerative Processes in Breathing Tubes of 
J anellidse.lT — Prof. L. Plate has been studying the remarkable New 
Zealand slugs ( Janella schauinslandi and Aneitella berghi) of the family 
J anellidas, in which the proper mantle-cavity is reduced and non-vascular, 
but gives off a large number of arborescent thin-walled tubules project- 
ing into a blood-sinus surrounding the cavity. In these tubes there is 
an intense cellular disruption, perhaps due to the fact that the respira- 
tory cells have also to keep the tubes moist by secreting mucus. The 
dying cells are for the most part extruded into the sinus dorsalis , where 
they are destroyed by phagocytic blood-corpuscles and plasma-cells, or 
partly dissolved. In both species described the nuclei of the cells in 
question are remarkable in being much lobed. The most interesting 
fact, however, is that the replacement of these used-up cells occurs by 
direct division. Here we have a clear case of a specialised tissue in 
which direct nuclear division is regenerative. 
* Zool. Jahrb. (Abtli. Syst.), x. (1897) pp. 596-608 (2 pis.), 
t Abh. Senckenberg. Nat. Gesell., xxiv. (1897) pp. 1-14 (3 pis.), 
f Tom. cit., pp. 19-92 (8 pis.). § Tom. cit., pp. 97-130 (2 pis.). 
H Tom. cit., pp. 137-44 (1 pi.). 
1 Arch. Mikr. Anat., li. (1898) pp. 839-56 (1 pi.). 
