BULLEIIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
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between Callidina and Eosphora, as described by Tessin. Nevertheless 
it is possible that the slight time variation in the cleavage of Eosphora 
may have misled Zelinka as to the point which needed especial care. 
In Asplanchna Herrickii and Asplanchna priodonta, in Melicerta and in 
Callidina, the large cell du divides first, followed immediately (in all 
except Callidina, at least,) by the division of d*?. In Eosphora, by a 
slight relative delay of the cleavage in % (a, Tessin), the cell % (a, 
Tessin) divides first. Zelinka states that he has observed with especial 
care that tho first cell (IV, Zelinka) given off in this quadrant takes 
origin from d** (I, Zelinka). This is doubtless true; the important 
point, however, is the origin of the next cell formed. Though this also 
is stated to arise from the ventral cell of the series (I, Zelinka), it 
seems possible that Zelinka was thrown off his guard by the supposed 
greater care necessary for determining the exact method of the preced- 
ing cleavage, and that the statement with regard to this one is really a 
mistake. The cell IV in Figure 23 (Taf. II.) of Zelinka's work might 
be the same cell as V in his Figure 24, while the cells called III and IV 
in Figure 24 might have arisen by the division of the previously exist- 
ing cell III (= 4*7) This would bring the conditions in Callidina 
into agreement with those in Eosphora, Melicerta, and tho two species 
of Asplanehna. This is, of course, a mere suggestion, which indeed is 
rendered rather improbable by the nuclear conditions in the cells under 
discussion shown in Zelinka's Figure 24. There can, of course, be no 
question about the manner of division in Asplanchna, Figure 16 (Plate 
2) shows the spindles in & and d^?, and the accomplished division of 
d^! into d^! and d*? is shown in Figure 19 (Plate 3), while d*? still 
contains a spindle. I have observed similar conditions in many other 
specimens. 
In view of the essential similarity of the process in Eosphora, as 
described by Tessin, to that in Melicerta, as described by Zelinka, and 
in the two species of Asplanchna, as observed by me, and in view of the 
fact that the cleavage of the quadrant in question (D) in these four 
forms may be said to agree completely with the general plan of cleavage 
as exhibited in the other three quadrants, — while in Callidina the con- 
ditions in this quadrant are anomalous, — the following remark of 
Zelinka (91, p. 61) seems hardly justifiable: “ Da, wie später gezeigt 
wird, auch Melieerta in der Entwicklung unserer vorliegenden Form 
folgt, so muss der Vorgang bei Eosphora als eine bemerkenswerthe 
Verschiedenheit aufgefasst werden.” As above shown, the difference 
between Kosphora and the other forms consists merely in a slight 
