ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
190 
The first segments are short, but they very soon (eighth or tenth) show 
traces of reproductive organs. Genital pore unilateral. The posterior 
limit of each segment is sharply defined, and forms an angle of about 
45 degrees with the sides. Egg spherical, diameter about 40-50 /x. The 
three pairs of embryonic hooks measure about 20 /x each in length. 
Incertae Sedis. 
New Genus of Enteropneusta.*— Dr. A. Willey describes Spengelia 
porosa g. et sp. n., from Lifu, Loyalty Islands : — “ If it were not for 
the presence of vestigial roots in the collar nerve-cord, Spengelia (apart 
from its own peculiar features, e.g. dermal pits, splanchnic layer of 
Punldsubstanz, accessory genital pores not perforating the longitudinal 
musculature, &c.) might almost be defined as a Glandiceps, with synap- 
ticula between the branchial bars.” 
The genera of Enteropneusta fall naturally into three groups : — 
Group I., including Ptychodera, briefly characterised by the presence of 
an outer layer of circular muscles in the integument of the trunk, the 
occurrence of dorsal roots putting the fibrous layer of the collar nerve- 
cord in connection with the fibrous layer of the epidermis ; and the pre- 
sence of liver-saccules and of synapticula between the branchial bars. 
Group II., including Schizocardium, Glandiceps , Spengelia , charac- 
terised by the presence of an inner layer of circular muscles (inside the 
longitudinal layer) and by the occurrence of a long vermiform process 
extending forwards from the anterior end of the notochord or proboscis 
caecum. 
Group III., including Balanoglossus, characterised by the absence 
of circular muscles in the integument of the trunk, and by the absence 
of synapticula. 
Fertilisation in Myzostoma.f — Herr K. Kostanecki has investigated 
the maturation and fertilisation phenomena in Myzostoma glabrum. His 
main conclusion is a corroboration of Boveri’s generalisation that the 
centrosomes of the first cleavage spindle arise from the sperm-eentro- 
some. It was thought that Myzostoma was exceptional in this respect ; 
but Kostanecki has shown that it is normal. There need be little 
hesitation, he says, in extending the generalisation to all Metazoa. 
Rotifera. 
Impregnation of the Ova of Hyaatina Senta.J — According to 
Dr. Sadone’s observation, the spermatozoa of the male Hydatina, which 
are injected into the body-cavity of the female, reach the totally enclosed 
eggs by boring through the thin membrane of the ovary at a point where 
the mature ova are situated, a process which is not known in any other 
class of animals. The oval head of a spermatozoon was seen to attach 
itself to the membrane of the ovary, while the tail continued to make 
lashing movements in the body-cavity until the head was gradually 
forced through the membrane followed by the tail ; the whole process 
taking eight to ten minutes. It is probable that this process is the same 
in other Rotifers. 
* Quart. Journ. Micr. Sci., xl. (1898) pp. 623-30 (1 pi.). 
f Arch. Mikr. Anat., li. (1898) pp. 461-80 (2 pis.). 
X Zool. Anzeig., xx. (1897) pp. 515-7. 
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