738 The American Naturalist. [August, 
structures indicative of wider or more general affinities with other 
Bilateralia. The summary given below is in his own words. 
1. The arthropod egg is not to be regarded as centrolecithal and 
having a superficial segmentation, but as having a central segmenta- 
tion, the blastoderm being formed by migration of the resulting cells to 
the surface. 
2. The primitive groove in the arthropods is a modified blastopore, 
and the absence of invaginated entoderm in some forms is to be ex- 
plained by Cope's and Hyatt's theory of acceleration and retardation. 
3. In Crangon the anus occupies the position of the blastopore. 
4. In Crangon and many other Crustacea the young germinal area 
is actually larger than the much older embryo. 
5. All of the appendages belong to the primitively post-oral series, 
and the appendages move forward more rapidly, than the correspond- 
ing ganglia. 
6. There are indications of segmental sense organs in every segment 
of the body. 
7. The alimentary tract proper is nearly, if not entirely, formed 
from the proctodeal and stomodeal invaginations, the entoderm giving 
rise to nothing but the liver. 
8. The green gland is mesodermal in origin, and belongs to the 
category of segmental organs. 
9. The genital ducts are modified nephridia. 
10. The nauplius is an introduced feature, and represents no adult 
ancestral condition in the crustacean phylum. 
Development of Sepia officinalis. — M. L. Vialleton concludes 
in the Annates des Sciences Naturelles (Tome VI., Nos. 4, 5, 6), an 
important contribution to the knowledge of the early phases of the 
development of Sepia officinalis, illustrated by six plates. 
The formative vitellus in the Sepia is reduced to a laminae at the 
pointed end of the yolk, and in this laminae, directly after fecunda- 
tion, a germinative central disc can be distinguished The first plane 
of segmentation is meridional, and divides the disc into five equal parts. 
Two and finally four secondary meridional divisions fin&lly divide it 
into eight unequal segments. The polar globules place themselves near 
the first furrow at some distance from the centre of the egg. These 
eight segments have the value of macromeres. In the fourth stage the 
two inferior segments are divided equatorially, the others meridionally, 
dividing off two micromeres, so that the blastoderm at this stage has 
fourteen macromeres and two micromeres. By a further bipartition, 
