SUMMARY OF CURRENT RESEARCHES RELATING TO 
556 
chief result is that there exists an alternation in the direction of the 
spirals in successive generations. The spirals of the even generations 
are right spirals, those of the odd generations arc left. The alternation 
is demonstrable in many forms of spiral cleavage, and it rests on the 
more fundamental and wide-spread tendency of the spindle to take a 
position at right angles to that of the spindle of the previous division. 
Mr. Kofoid also points out that one must consider not only the quantity 
of the yolk, but the quality of both yolk and protoplasm, in comparing 
different modes of cleavage. 
Primitive Nephridia of Lymnseus.* — Dr. E. v. Erlanger describes 
the paired excretory organs of larval freshwater Pulmonates. Each is 
a Y-shaped canal, opening externally by an oval aperture near the anus, 
opening internally into the body-cavity. Each consists of several cells 
— not of one as Wolfsohn says — and the cell at the corner of the Y is 
very large. The excurrent part, up to the large cell, is ectodermic, the 
inner part mesodermic. From the spoon-shaped internal funnel an 
undulating membrane runs down the afferent part of the nephridium. 
The internal aperture is lateral, not terminal. 
Peltella.t — Dr. IT. von Jhering gives an account of the structure of 
Peltella palliolum. He distinguishes the genus from Parmacella, with 
which it has been confused, and shows its great affinities with Bulimulus , 
of which, indeed, it almost appears to be a direct modification. 
Renal and Circulatory Organs of Chitons4 — Dr. L. Plate in some 
further § observations says that he has found confirmation of his view that 
B. Haller’s description of the hinder tip of the ventricle opening into 
the connecting piece of the two auricles cannot be correct. In two 
species he found the median renal duct completely absent from the foot, 
and it is possible that it was not present in the species dissected by 
Haller and Sedgwick, neither of whom mention it. 
Oncidiella coquimbensis.|| — Dr. L. Plate gives an account of this 
new species from the coast of Chili, where it is not rare. The edge of 
the mantle is, contrary to rule, smooth ; the coloration is extremely 
variable. The internal organization exhibits nothing specially note- 
worthy. This sp>ecies is allied to Huppe’s Oncidium chilense which is 
probably a true Oncidiella. 
8 . Lamellibranchiata. 
Systematic Position of Trigonidae.^F — Dr. S. von Wohrmann finds 
that the Trigonidarj and Najadae ought not to form a special group of 
Schizodonts, but should be associated with the Heterodonts. The 
Najadse are either marine (and extinct) or fresh-water forms, like Vnio. 
Though there are certainly relations between the Unionidee and Trigonia , 
they are not derived from it. 
* Biol. Centralbl., xiv. (1894) pp. 491-4 (2 figs.). 
t Arcliiv Mus. Rio de Janeiro, viii. (1892) pp. 135-53 (2 pis.). 
X SB. Akad. Wiss. Berlin, 1894, pp. 217 and 8. § See ante, p. 440. 
|| SB. Akad. Wiss. Berlin, 1894, pp. 218 and 9. 
•ff JJ3. K. K. Geolog. Reichsanstalt Wien, xliii. (1893) pp. 1-28 (3 pis.). See Zool. 
Centralbl., i. (1894) pp. 75 and 0. 
