1880. ] Development of Amphioxus lanceolatus. 79 
figured by Joh. Miller’ and considered by him to be the anterior 
openings of the meta-pleura. In the case of the female which 
was in my possession, the ova were extruded very gradually and- 
for the most part one by one, so that here and there along the 
row of cases could be seen, one with a single ovum gone, others, 
nearer the ends, half empty, and still others, near the middle, 
with their full quota. During this period, which extended over 
the entire time the animal remained alive, I was not fortunate 
enough to see any ova leave the body, but from the size of the 
branchial slits, the position of the generative bodies, and the 
actions of the cilia, currents and abdominal walls, which I studied 
with considerable care, I arrived at the conclusion, which is in 
accordance with the opinions of Wm. Müller, Quatrefages, &c., 
that, the ova all passed from the body by the branchiopore, and 
that while not absolutely impossible, it would be an exceedingly 
exceptional proceeding if any should pass out by way of the 
mouth. I found that seven ova placed side by side extended 
Over a space just equal in length to the breadth of five branchial 
slits with their enclosing arches, and as the bars of the arches are 
quite as broad as the slits, the ova in passing out in this direction 
would be obliged to pass in opposition to the powerful action of 
the branchial cilia and inflowing water, through openings which 
at most would be only seven-elevenths as broad as the diameter 
of a single ovum, which would be an exceedingly difficult per- 
formance. If the openings mentioned by Prof. Lankester exist, 
and are no broader than the breadth of the branchial slits, there _ 
would be the same difficulty in passing through them as in 
forcing a way through the slits, besides having to traverse nearly — 
half the length of the pharynx against the current of water and 
the pressure of the abdominal walls. If these openings are 
larger than the openings of the slits, it would hardly seem possi- 
ble that they could have remained undetected until this late _ 
date, but even in this case the passage of ova through them — 
could hardly be more than an occasional and chance occurrence, 
since the same obstacles exist to the passage of the ova forward a 
to these openings as in the case of the smaller ones, and are even 
increased by the liability of currents of water setting through 
them into the branchium and thus assisting in expelling the ova- SS 
* Ueber den Bau und die Lebenserscheinungen des Branchiostoma lubricum. Von 
Joh. Müller. Abhandlungen der Berliner Akad. Berlin, 1842 (1844), Pl. 11, Fig. 
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