File:EB1911 Peripatus - Series of Embryos.jpg

DescriptionEB1911 Peripatus - Series of Embryos.jpg	English: A series of diagrams of transverse sections through Peripatus embryos to show the relations of the coelom at successive stages. See legend below.
Date	published 1911
Source	“Peripatus,” Encyclopædia Britannica (11th ed.), v. 21, 1911, p. 167, fig. 12.
Author	After Sedgwick.
Permission (Reusing this file)	Public domainPublic domainfalsefalse This image comes from the 13th edition of the Encyclopædia Britannica or earlier. The copyrights for that book have expired in the United States because the book was first published in the US with the publication occurring before January 1, 1929. As such, this image is in the public domain in the United States.

A, Early stage; no trace of the vascular space; endoderm and ectoderm in contact.

B, Endoderm has separated from the dorsal and ventral ectoderm. The somite is represented as having divided on the left side into a dorsal and ventral portion.

C, The haemocoele (3) has become divided up into a number of spaces, the arrangement of which is unimportant. The dorsal part of the somite has travelled dorsalwards, and now constitutes a small space (triangular in section) just dorsal to the gut. The ventral portion (2) has assumed a tubular character, and has acquired an external opening. The internal vesicle is already indicated, and is shown in the diagram by the thinner black line: 1, gut; 2, somite; 2′, nephridial part of coelom; 3, haemocoele; 3′, part of haemocoele which will form the heart—the part of the haemocoele on each side of this will form the pericardium; 4, nerve-cord; 4, slime glands.

D represents the conditions at the time of birth. The coelom is represented as surrounded by a thick black line, except in the part which forms the internal vesicle of the nephridium.