SOME POINTS IN THE ANATOMY OF THE PLATYDESMID®. 517 
that I have examined do not seem to me to be such as to 
warrant their being included in a sub-order with these 
characters. The small head, the free lamina pedigera, and 
simple copulatory organs are the only characters which 
agree with the definition, and these are common to other 
groups. The mandibles, hypostoma, and upper lip do not 
form a suctorial apparatus. The peculiar arrangement of 
bristles on the mandible point rather to a carnivorous diet 
than to a liquid, and there is no apparatus for piercing in 
order to obtain liquid nourishment. Compare the hypostoma 
with that of the other groups of the Colobognatha, and with 
that of Polydesmus, and it must be admitted that it most 
resembles that of Polydesmus. The want of foramina 
repugnatoria, if I am correct in my belief that they are 
absent from the Platydesmidz, separates them from the 
Colobognatha as does the peculiar arrangement of the body- 
ring on the pentazonal plan. In the internal organs I can 
see no signs of degeneration. Verhoeff, however (‘ Zool. 
Anz.,’ xxiv, No. 654, 1901), denies that the Colobognatha 
are degenerate forms. The nervous system, to which I have 
devoted most attention, seems to me to be quite as well 
developed as that of the Polydesmide, and to resemble the 
latter to a great extent. 
When we come to consider what group the Platydesmide 
should be placed in, it is a harder question, and one that I 
feel myself little qualified to solve. I shall therefore content 
myself with saying that until evidence to the contrary is 
forthcoming I shall regard the Platydesmide as an 
aberrant group allied, as Gervais supposed, to the Poly- 
desmidez. 
With regard to more general considerations, the nervous 
system has interested me deeply, and has led me to dissect 
a great quantity of Diplopod brains. I hoped that these 
dissections might have thrown some light upon a question 
that most naturalists, I believe, consider already settled, the 
question of the unity of the group of Myriapoda. My 
investigations, though they do not in any way settle the 
