210 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
[Maturation and Fertilisation in Prosthecerseus vittatus.* — Dr. A. 
von Klinckowstrom describes these processes in the ova of this large 
marine Planarian, which appears to afford very excellent material for 
such studies. About half an hour after oviposition the first polar body 
is given off. It shows active amoeboid movements for four or five hours. 
Two or three hours after the first the second polar body is given off. 
In an hour or two the cleavage is in active progress ; in 15-20 hours the 
16-cell stage has been reached. The peculiar nuclear metamorphosis 
which Selenka described in Thysanozoon does not occur in Proslhecerseus ; 
the division-figure in the uterine ovum is simply the first directive 
spindle. The author gives the following scheme of the maturation- 
process, the letters meaning chromosomes, of which there are typically 
twelve, admitting of 853,776 possible combinations in fertilisation : — 
, ... Id ) 
I 1st directive spindle with six 
l bivalent chromosomes. 
I’ •* ' Yin 
— - — equation division 
I 
a b , c cl, ... Id \ 
f 2nd directive spindle with 
/« c k\ | reduction division 
V cV in 
m , n, o, p , q , r a, c, e, g, i, h b, cl, ... I 2nd polar body 
male pronucleus female pronucleus 
m, n, o, p, q, r, a, c, e, g, i, 1c 1st cleavage spindle. 
Male Organs of Stenostoma leucops 0. Schm.f — Herr H. Sabussow 
points out the defectiveness of our knowledge in regard to the reproduc- 
tive organs of Turbellarians. He sets himself to remedy this by a 
careful description of the male organs of Stenostoma leucops O. Schm., 
which consist of five parts — an unpaired testis, an almost spherical 
vesicula seminalis, a tubular penis without chitinous parts, a penis- 
sheath, and a small antrum masculinum. 
Hew Ectoparasitic Triclad4 — Herr L. A. Jagerskiold describes 
Micropharynx parasitica, found on Baja clavata and B. batis. It is a 
quite typical Triclad, without marked adaptation to ectoparasitic life, 
except that it has no eyes, thus differing, inter alia, from the other para- 
sitic Triclad Bdelloura limuli v. Graff. 
a b, ci 
/ah c 
V7V c 
ab, cd, ... Id 
1st polar body 
* Arch. f. Mikr. Anat., xlviii. (1897) pp. 587-605 (2 pis., 3 figs.), 
t Zool. Jahrb. (Abtli. Syst.), x. (1897) pp. 47-54 (1 pi.). 
X Ufversigt K. Yetensk. Akad. Forhandl., 1896, pp. 707-14 (3 figs.). 
