ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
521 
Anatomy and Development of Scorpions.* — Prof. M. Laurie lias con- 
tinued liis examination of various typical genera of Scorpions, with a 
view to the investigation of their bearing on the classification of the 
order. He is more than ever convinced of the great value of the mode 
of development as a basis for classification, and is inclined to consider 
the structure of the lung- hook lamellae of subordinate though considerable 
value. The terms Mr. Laurie has hitherto used to define the two chief 
types of development will no longer serve, because there are so many 
variations from the type in each case, that to speak of Scorpio and 
Euscorpio types of development is misleading. The fundamental dif- 
ference is, that in the latter the egg early leaves the follicle in which it 
is formed, and passes into the cavity of the ovarian tube. In the other 
case, the eggs divide in situ, and as the embryo becomes too large for the 
follicle, it extends down and occupies a diverticulum from the ovarian 
tube, at the distal end of which the egg is originally formed. The 
author suggests the terms apoikogenic and katoikogenic as adequately 
designating the two methods. So far as observation has gone, the 
members of the family Scorpionidee are all characterised by the katoiko- 
genic mode of development ; the other families — Iuridse, Bothriuridae, 
and Buthidae — are apoikogenic. The latter type of develojnnent appears 
to be the more primitive. It is only one step from the laying of the 
eggs which is the almost universal custom among Arthropods. With 
regard to the structure of the lung-books, Mr. Laurie is inclined to regard 
the so-called spinous type as the original. More evidence is wanted 
before we can judge of the true relation of the various sub-families of the 
Scorpionidae to each other, and the author is afraid that he has perhaps 
tried to base too much on a comparatively small number of observations. 
e. Crustacea. 
Nervous System of Crustacea, f — Mr. E. J. Allen continues his 
studies on the nerve-elements of the embryonic lobster. He deals first 
with elements arising from cells situated in the thoracic, and next with 
those which arise from cells situated in the abdominal ganglia. The 
motor elements found in the abdomen in nearly every case supply fibres 
to the posterior nerve-roots of the ganglia, while the greater number of 
those described for the thorax, in this and the author’s previous paper, 
send their fibres to the anterior nerve-roots, a few only supplying the 
posterior roots. The probable reason for this difference is not, Mr. Allen 
thinks, difficult to find. The anterior roots chiefly supply the appen- 
dages, which are well developed in the thorax of the embryo, while in the 
abdomen they are wanting. The posterior roots, on the other hand, 
supply the muscles of the body itself, which are well developed in the 
abdomen, but less so in the thorax. 
Abnormal Crab.f — Mr. A. Betheifound at Plymouth a crab with a 
large leg on the left side of the fifth segment of the abdomen. This 
leg was at once seen to be a real walking leg, and not a left-handed but 
a right-handed one ; compared with other walking legs, it was seen to 
correspond to the second and third of the thorax. When alive the leg 
* Ann. and Mag. Nat. Hist., xviii. (1896) pp. 121-33 (1 pi.), 
t Quart. Journ. Micr. Sci., xxxix. (1896) pp. 33-50 (1 pi.). 
X Journ. Mar. Biol. Assoc., iv. (1896) pp. H4-5 (1 fig.). 
2 o 
1896 
