620 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
to the following conclusions: — (1) The larval and the persisting nervous 
system arise from the same rudiment as the hypophysis, viz. the original 
ectodermic invagination which forms the cerebral vesicle ; (2) the larval 
cerebral vesicle is, during the later larval period, in communication 
with the gut through the future hypophysis ; (3) the anterior part of the 
hypophysis arises directly from the anterior region of the elongated 
cerebral vesicle, the posterior part from the left epithelial wall of the 
same ; (4) the lumen of the hypophysis is, in the adult, the only per- 
sisting residue of the larval cerebral cavity ; (5) the persistent brain of 
the adult arises from the thickening of the left wall of the cerebral 
cavity from which the hypophysis grows out. 
y. Brachiopoda. 
New Classifications of Brachiopoda.* — Miss Agnes Crane has a 
critical notice of some recent modifications in the taxonomy of Brachio- 
pods. Mr. C. Schuckert has published in the * American Geologist ’ 
(xi. 3) a classification “based on the history of the class (chronogenesis) 
and the ontogeny of the individual.” Beecher’s suborders of Atremata, 
Neotremata, Protremata, and Telotremata are adopted as orders; the 
Protremata are divided into the Trullacea and the Thecacea ; in all nine 
new families are added. Mr. C. E. Beecher published, in March last, 
a “ revision of the families of loop-bearing Brachiopods ” ; he divides 
the Terebratellidse into the three well-defined families of Dallininae, 
Magellaniinas, and Megathyrinm. Both branches of the Terebratellidae 
appear to have originally sprung from some minute form allied to the 
existing Gwynia, which, doubtless, lived before the Jurassic period, and 
to which palaeontologists should turn their attention. Miss Crane con- 
siders that the advances in our knowledge of the genealogy of the recent 
Brachiopods are such as to have brought us to a turning-point in the 
history of the race. 
Arthropoda. 
Classification of Tracheate Arthropoda.t— Mr. R. I. Pocock urges 
that the Tracheata may be considered to consist exclusively of the 
Myriopoda and Hexapoda, and inquires whether the group, as thus 
limited, is a natural one. After pointing out the well-known characters 
which the two classes have in common he remarks that the division into 
Myriopoda and Hexapoda is based principally upon the external form. 
On further examination, however, it is clear that the so-called group of 
Myriopoda is sharply divisible into two sections upon a character 
which admits of no exception. This character is the position of the 
generative organs. In the Pauropoda and Diplopoda the genital orifices 
are situated near the anterior end of the body, while in the Chilopoda 
and Symphyla ( Scolopendrella ) they are placed at the posterior end, 
quite close to the anus ; this latter position is that which is seen also in 
the Hexapoda. Now various writers have pointed out that Scolopendrella 
is closely related to the Thysanura, and the author remarks, no one who 
compares a Scolopendrella with a Chilopod on the one hand and with a 
Thysanurous Hexapod, on the other can avoid being struck by the fact 
that the differential characters between the Insects and the Centipedes 
* Geol. Mag., x. (1893) pp. 818-23. f Zool. Anzeig., xvi. (1893) pp. 271-5. 
