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ON THE CLASSIFICATION OF THE ASCARIDAE. 
II. THE POLYDELPHIS GROUP; WITH SOME ACCOUNT 
OF OTHER ASCARIDS PARASITIC IN SNAKES. 
By H. A. BAYLIS, M.A. 
(Published by permission of the Trustees of the British Museum.) 
(With 7 Text-figures.) 
The Ascarids parasitic in snakes present considerable difficulties from the 
systematic point of view, owing to the incomplete character of many of the 
descriptions, and to the state of confusion which has long existed in the 
nomenclature. The writer has made an attempt, by examining such material 
as was available, and by comparing a number of the existing descriptions, to 
clear up some of this confusion. It was hoped also that such a comparative 
treatment would throw some light on the systematic value of the modifications 
of the female genital apparatus, which occur in some of these forms. 
The typical female Ascaris, as is well known, possesses two uterine branches, 
commonly running backwards and parallel to each other from their point of 
origin in the common uterine tube. Retzius, in 1830, was the first to describe 
a multiplication of the uterine branches, occurring in an Ascarid from the 
python, subsequently redescribed and named Ascaris anoura by Dujardin 
(1845). In this form the uterus is divided into four, instead of two, branches, 
and Dujardin regarded it as representing a sub-genus, which he named 
Polydelphis, of the genus Ascaris. Since that time other forms having a four- 
branched uterus have been described from snakes. It was not, therefore, very 
surprising to the writer to discover, in 1916, an Ascarid from a snake showing 
a still further increase in the number of uterine branches. This was A. bod- 
daertii Baird, in which the branches were found, on re-examination of the type, 
to be six in number. About the same time Cedoelst (1916) described a form, 
Ascaris hexametra, from a chamaeleon, in which a similar structure was seen; 
and more recently the writer has observed the same modification in two more 
Ascarids from snakes. 
The Ascarids of snakes seem, as far as can be ascertained at present, all to 
belong to the sub-family Ascarinae. They show remarkably few characters 
which can be regarded as of more than specific value, in the present state of our 
knowledge of the Ascarid family as a whole. Most of them, however, appear to 
fall into two fairly well-marked groups, which may, provisionally at least, be 
treated as genera. 
Parasitology xn 
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