ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
165 
nective tissue, and to pass among the ciliated cells. These last will 
soon show distinct signs of change ; their protoplasm appears to have 
been gnawed out where it lias been in contact with a leucocyte. In this 
way there may be formed large lacunae in which move a more or less 
large number of leucocytes, each playing tho phagocyte on its own 
account ; the bodies of these cells often increase in size considerably. 
In specimens preserved with Flemming’s or Hermann’s fluid the 
author has often been able to demonstrate the presence of degenerate 
leucocytes, either in the phagocytes or in the tissues ; although found in 
the most varied forms, they are always composed of an irregular element 
which stains slightly or not at all, and which serves as the substratum 
for one or more safraninophilous cells; the substratum was of proto- 
plasmic origin, while the chromatic element was derived from the 
nucleus. The author comes to the conclusion that we have here to do 
with another example of the continual strife between the cells of a single 
organism and the removal of weakened, discarded, or dying anatomical 
elements by amoeboid cells which are still in full vital activity. The 
ciliated cells of the lower edge of the branchial lamellae are, by their 
very situation, exposed more than any other to every kind of destructive 
cause; they are, therefore, rapidly weakened and used up, and their 
weakened bodies have an attraction for the leucocytes. 
South American Najadse.* — Prof. H. von Jhering has made a study 
of the Najadae (= Unionidae and Mutelidae) of S. Paulo. Between TJnio 
and Castalia he finds that Castalina g. n. is transitional, and the three 
genera might be united. In S. American Najadae it is the inner gill- 
plate which shelters the embryos. A Glochidium larva occurs in South 
American forms, in TJnio, Castalina , Castalia , and perhaps in Lyria , but 
it cannot be said that the S. American species of Unio have the same 
development as those of Europe. The peculiar Lasidium larva of 
Glabaris is described. Then follow notes on the hinge-teeth, &c. Yon 
Jhering characterizes as Mutelidae those which have a Lasidium, as 
Unionidae those which have a Glochidium. 
The descriptive part of the memoir takes account of 30 species, of 
which Glabaris Nehringi, Fossula Balzani, Plagiodon Balzani , Castalina 
Nehringi, C. Martensi , Unio paulista, TJ. Greeffeanus , U. Caipira , U. 
Martensi , U. Frenzellii are new. 
Yon Jhering concludes with a long discussion of the “ Archiplata ” 
freshwater fauna, so puzzling in its distinctness from the rest of 
South America, and in its relations with Australia and New Zealand, 
and even with Africa. In regard to the last point, he postulates an 
ancient land connection between Africa on the one hand and Brazil and 
Guiana on the other. 
Molluscoida. 
a. Tunicata. 
Studies on the Protochorda .f — Mr. A. Willey, in his first memoir 
under this title, discusses the origin of the branchial stigmata, praeoral 
lobe, endostyle, atrial cavities, &c., of Ciona intestinalis , and has some 
remarks on Clavelina lepadiformis. He has completely altered his views 
as to the homologies between the various organs of the Ascidians and 
* Arch. f. Nature, lix. (1893) pp. 45-140 (2 pis.), 
f Quart. Journ. Micr. Sci., xxxiv (1893) pp. 317-60 (2 pis.). 
