BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
CLEAVAGE OF APLYSIA. 
BLOCHMANN'S NOMENCLATURE. 
Blochmann (88). 
REVISED NOMENCLATURE. 
Number 
f 
Gener- © 
TREE EEE EHE ET MR ED ation. Cells, E Le eT E Er TE RTI. C "dc 
Spirals. Cells, Cells, Spirals, 
a 
PER dy ERORE ro 08 me ts Left 
[M 6.2 a Meridional 
b, > bs VIL. < at? | slightly left. 
; Pr 
P — > b age hie Ald Left. 
b , 5 une í 
ta ¡De ba 20 ab? <G 6-8 Right. 
n VI. 23i 
; 5 a” 
je >) gos | <L VIE Right. 
by Vv A‘ ad? 
Left. „ob 12 < Asa Left 
j b, EHE ; 
Right. pb IV; go Tn VIE Right. 
III. 4 A, B, C, D. Left. 
e T AB, CD. 
In the above table the labelling of cells indicated in the second col- 
umn is that given by Blochmann to cells which seem to be homologous 
with those of quadrant 4. 
The cleavage of Aplysia, so far as followed by Blochmann, resembles 
very closely that of Umbrella. If we interpret the cleavage as Heymons 
has that of Umbrella, we find that here also the posterior and smaller 
cell of the two-cell stage divides first; the mesoderm quadrant D 
