0LIG0CH2ETA, HIRUDINEA. 
Verm. 33 
to such an extent that the mother-periplast becomes divided into two 
daughter-periplasts, each surrounded by striae of cytoplasm and con- 
nected together by cytoplasmic fibrillae, in the midst of which lies the 
now fusiform male pronucleus. There are thus two spindle-like struc- 
tures produced, viz., the periplastic spindle, lying, so to speak, inside a 
cytoplasmic spindle. Female pronucleus now wanders to centre of egg 
and comes into contact with the male pronucleus. Author has not actu- 
ally observed the fusion. A remarkable feature in the ovum of Rhyn- 
chelmis is the preponderating size of the male pronucleus over that of the 
female. This is the only such instance yet described. The two elements 
are usually of equal size, while in Echinoderms the female is the larger 
(0. Hertwig). Author adds : “ Bei Rhynchelmis ist es aber evident dass 
der mannliche Vorkern die Hauptrolle spielt ; er ist das thatige Element, 
welches auf den weiblichen Pronucleus einwirkt.” Main result of 
author’s observations is that the periplast, or “ attractionssphare,” is 
derived from the spermaplasma. The periplast prepares the way for the 
first segmentation of the egg by the formation of the above mentioned 
periplastic spindle, at a time whon the male and female elomonts have 
not yet fused. Author says : “ Meine Auffassung des Befruchtungs- 
vorganges lautet also dahin, dass wahrend der Polzellenbildung das thei- 
lende Element — der Periplast — aus dem Eie fast spurlos eliminirt wird und 
demnach durch das Spermaplasma in Form eines neuen, energisch sich 
theilenden Periplastes ersetzt werden muss.” The second Heft deals with 
the later stages. The gastrula of the Lumbricidce is described as a pachy- 
gastrula. It is solid, and consists of hypoblast, arranged in two layers 
without a cavity between them ; while the epiblast covers three-quarters 
of the surface. It is, therefore, very far from being an “ archigastrula.” 
Author has only been able to see one pair of teloblasts, which gives rise 
entirely to the mesodermic bands. Some pages (250-269) are devoted to 
observations on occurrence of double embryos in the Lumbricidce. Author 
has observed formation of twins in Lumbricus terrestris, A.fcetida, and A. 
trapezoides. In the latter case it is very common, but not universal, as 
Kleinenberg assumed. An explanation of the plates of any sort, as also 
pis. xxi & xxii, are conspicuous by their absence. They may appear in 
the next Heft. 
HIRUDINEA. 
New Genus and New Species. 
Clepsinc car inala, plana, Massachusetts, Whitman (1, 2), n, spp. 
v Pseudobranchellion, n. g., for P. margdi, n. sp., Naples ; ApAtiiy (1). 
New Descriptions, Synonyms. 
Blanchard (3). Limnatis nilotica, Savigny, 1820. 
Lang. Hcementaria ghilianii , F. de Filippi. 
