ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 777 



is broad, and the tentacles and rhinophores conical ; the new species 

 is called G. borealis, and it, like Campaspe major sp. n., is at present 

 represented by a single specimen only. 



Lamellibranchs of the ' Willem Barents.' *— Dr. J. T. Cattie 

 gives a systematic list of the thirty Lamellibranchs collected during 

 the ' Willem Barents ' expedition in 1880 and 1881. In the succeeding 

 anatomical portion he first discusses the nature of the byssogenous 

 organs in several species. The observations of Reaumur on the mode 

 of attachment of mussels are most exact, and those which the author 

 has been able to make on Dreyssena polymorplia are almost identical 

 with what both observed in the mussel. He finds that the formation 

 of the byssus is a very simple process ; the walls in the lamellae of 

 the byssiferous cavity incessantly secrete a byssogenous material. 

 The lamellae in the anterior part of the cavity, which is the narrowest 

 in Mytilus, unite and fuse with one another, and since the orifice is 

 fctill more narrow, they form the round tendon of Reaumur, or what 

 Dr. Cattie calls the trunk of the byssus. When, as in Dreyssena 

 pulymorpha and Modiolaria discors, the orifice is not so well marked, 

 or the lamellae more irregularly arranged, transverse sections show 

 that the lamellae of the byssogenous material are twisted, and that 

 they alternate with the lacunae. As the ventral groove of the foot 

 opens into the byssiferous cavity, and the glands secrete their material 

 at the same point, it is clear that each byssus-thread which is formed 

 in the groove is at once fused with the trunk of the byssus. 



The ventral groove and the byssiferous cavity are clothed with an 

 epithelium, which is in most cases ciliated ; around them there are 

 grouped glandular cells, the body and nucleus of which are converted 

 into a granular refracting mass. An increase of surface is gained by 

 the development of longitudinal folds, and the number of these 

 lamellae is considerable in the Mytilidae and Pectinidae. 



With regard to the much disputed question as to the introduction 

 of water into the circulatory system of Lamellibranchs, the author 

 agrees with Carriere and Barrois that, if water does enter, it certainly 

 does not do so by means of the so-called pori aquiferi, for these are 

 certainly the orifices of more or less degraded byssogenous glands. 

 He agrees with Lankester that the supposed introduction would be a 

 somewhat startling physiological process ; the results of injections 

 must be borne in mind together with the motto, " Timeo injectiones 

 et nova ferentes." 



Molluscoida. 

 o. Tuuicata. 



Classification of the Tunicata.j — M. F. Lahille thinks that the 

 present systematic arrangement of the Tunicata is very artificial ; 

 after the presence or absence of a deciduous tail [which is regarded 

 by Gegenbaur as an unimportant character] the most important organ 

 for classification is the gill. The Salpidae have a single row of holes 



* Bijdragen tot de Dierkunde, xiii. (1886X48 pp. (4 pis.), 

 t Comptes Itendus, cii. (1886) pp. 1573-5. 



