ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
179 
sarcastic manner with Dr. Dendy’s assertion that Peripatus leuckarti is 
oviparous, and brings abundant evidence to show that tho species from 
New South Wales, which bears that name, is viviparous. Dr. Dendy * 
accepts this evidence but reiterates his assertion that the species which 
bears the same name in Victoria is oviparous, and he brings forward 
some fresh evidence in support of his assertion. Dr. Dendy points out 
that it was in deference to the judgment of others that he called the 
Victorian species P. leuckarti , and he refrains at present from giving a 
new specific name to the cause of a very lively discussion. 
5. Arachnida. 
Morphology and Classification of Arachnida.f — Mr. R. I. Pocock 
proposes to divide the Arachnida into two sub-classes — that of the 
Ctenophora, and that of the Lipoctena. In the former the embryo is 
provided with six pairs of abdominal appendages, the second of which 
persists in the adult as the pectines ; in the latter the embryo is not 
provided with more than four pairs of abdominal appendages, and the 
second are never retained as external organs in the adult. The Cteno- 
phora, of which the Scorpiones form the sole order, have, in the adult, 
four pairs of abdominal breathing organs in the form of lamellar tracheae, 
the abdomen is very long, the foot and sclerite has two poison-glands, 
and they are viviparous. The Lipoctena, on the other hand, have not 
more than two pairs of abdominal breathing organs, the abdomen is 
much shorter, there are no post-anal poison-glands, and they are usually 
oviparous. The second sub-class is divided into two main groups dis- 
tinguished by the first having the cephalothorax and abdomen separated 
by a deep constriction, the first abdominal sternite forms an operculum 
to the respiratory stigmata, and the breathing organs are lamellar 
trachese ; the first two of these characters are not seen in the second 
division, where, also, the tracheae are tubular. This first subdivision 
is called that of the Caulogastra, and contains as orders the Pedipalpi 
and the Araneae. The second subdivision falls into two groups, that of 
the Mycetophora (order Solifugae), in which there is a pair of respiratory 
stigmata between the fourth and fifth cephalothoracic appendages, and 
that of the Holosomata (orders Pseudoscorpiones, Opiliones, and Acari), 
in which there are no such stigmata, and the cephalothorax is covered 
by a continuous shield. 
After a few remarks on the classifications of Profs. Lankester and 
Thorell, the author examines the question whether any beneficial results 
can be ascribed to the structural modifications which he has traced through 
the Arachnida, from the Scorpiones to the Acari. Mr. Pocock thinks 
there is evidence that the replacement of pulmonary sacs by tracheae has 
taken place independently at least twice — once in the Dipneumonous 
Spiders, and once in e. g. the Pseudoscorpiones. This fact is of weight 
as weakening the evidence of the affinity between the Opiliones and the 
Pseudoscorpiones. The fact, at any rate, that these tubes have been 
developed twice in the same group bears very strong evidence as to their 
efficacy as breathing-organs ; they must be supposed to be better adapted 
for their purpose than lung-book trachese, and it is suggested that an 
* Proc. Linn. Soc. N.S.W., vii. (1892) pp. 267-76. 
