Paper, 'On the coincidence of the anus with the blastopore in the newt (Triton cristatus)' by Alice Johnson

Description

Johnson writes: 'In a paper lately published on “The Origin of Metameric Segmentation,” Mr Sedgwick mentions that he was led to conclude from surface views of a large number of stages that the blastopore of the newt (Triton cristatus) does not close, but persists as the anus. He suggested to me afterwards that I should attempt to test this observation by cutting sections of the embryos, and my results fully confirm what he previously stated. Scott and Osborn, in their account of the development of the newt, describe a posterior dilatation of the medullary canal, the sinus rhomboidalis, which remains open for some time after the rest of the canal has closed. They say that its folds enclose the blastopore, and that, therefore, when they come together, a neurenteric canal is formed. Their account of the exact date of the closure of the medullary folds in this region is a little obscure, but seems to indicate that the event takes place while the number of protovertebrae is quite small, and before the rudiments of the visceral arches and tail have appeared.'

Annotations in pencil and ink.

Subject: Zoology / Physiology

Received 15 May 1884. Read 29 May 1884. Communicated by Michael Foster.

A version of this paper was published in volume 37 of the Proceedings of the Royal Society as 'On the changes and ultimate fate of the blastopore in the newt (Triton cristatus)'.

Reference number

PP/5/9

Earliest possible date

1884

Physical description

Ink and graphite pencil on paper

Page extent

6 pages

Format

Manuscript