784 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
pedipalps there is in the early stages of development a pair of slight 
protuberances ; later on they disappear altogether. 
Relations of Acaridae to Arachnida.* — Mr. H. M. Bernard brings 
forward evidence to show that the “ degeneration ” of the Acaridse 
from the Arachnidan standpoint “ is almost purely quantitative, not 
qualitative.” In other words he regards them as Arachnids permanently 
fixed at a larval stage of development. Tetranyclius tiliarum is a rather 
primitive form which retains its segmentation, but seven segments found 
in other Arachnids are missing, and so far it seems to be a fixed larval 
form. The primitive nature of this Mite is further spoken to by its 
mouth-organs. Taking these and other facts the author urges that the 
Acaridm are Araneids fixed at a larval stage because of the many advan- 
tages which animals of such small size have over larger ones and on the 
following grounds : 
(1) On comparing the segmentation of a simple form of Acarid with 
that of an Araneid, seven abdominal segments in front of the anal are 
seen not to be developed, but those that are can be easily homolo- 
gized with a similar number of anterior segments of an Araneid. 
(2) It is clear that it is the abdominal part of the alimentary 
canal of the Araneid that is wanting in the Acarid. 
(3) The heart of Gamasus appears to be an Araneid heart arrested 
in its development, and the abdominal extension is the part that is 
wanting. 
(4) The only important difference in the ventral ganglionic masses 
is due to the greater development of the abdomen in the Araneid. 
(5) The large size of the eggs of Acarids seems to show that, 
while the animal has diminished in size, the eggs have retained more 
nearly the size of those of the original adult forms. 
(6) While the Araneids have book-leaf tracheae confined to the 
abdomen, the Acarids have purely tubular tracheae confined to the 
thorax. 
Mr. Bernard adduces some objections to the theory of the gill-origin 
of tracheae, and urges that, if we sever the Arachnida from the Tracheata, 
it will be necessary to assume four more or less distinct origins for the 
tracheae. 
Excretory Organs of Pantopoda.f — Prof. A. Kowalewsky points out 
that the uncertainty which exists among naturalists as to the correct 
systematic position of the Pantopoda makes every addition to our know- 
ledge of their structure interesting. His investigations commenced 
with staining the organs during life, but the only reagent which was 
found to act quickly is acid fuchsin, and the genera chiefly studied were 
Ammothea , Pallene, and Phoxichilus. 
In PTiox. vulgaris the glands, which lie in the body-segments, form 
pretty compact organs, but exhibit considerable individual variations 
in position and number. The author describes his sections, which he 
figures, and to which he refers in such a way as to make any general 
review impossible. For the present he abstains from offering any 
generalizations. 
* Journ. Linn. Soc. Lond., xxiv. (1892) pp. 279-91 (1 pi.), 
t Mem. Acad. Imp. St. Petersburg, xxxviii. No. 12, 9 pp. (1 pi.). 
