ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 501 



between them, and this intermediate space may be greater than the 

 diameter of the larva. In the cases in which the animal that produced 

 the gall had originally only one point of contact with the galli- 

 plastema, the further inclusion of the larva is due to an annular 

 investment of the plastema, which increases in extent and becomes 

 folded over it. A temporary contact on the part of the larva does 

 not produce a gall. The larva3 are fed by the development in the 

 gall of a tissue the cells of which have thin walls and contents rich 

 in oil and albumen. In their anatomical structure many of tbe 

 galls have characters which appear to be completely foreign to the 

 organization of the plants that nourish them. 



y. Arachnida. 



Anatomy of Phalangida.* — Dr. E. Bossier finds that the digestive 

 system consists of three portions, of which the spacious midgut is 

 provided with a large number of caeca ; the sucking action is pro- 

 duced by a layer of strong transversely-striated circular muscles, 

 which is only continued on to the more anterior portion of the 

 succeeding oesophagus ; the lumen of this latter region is almost 

 completely filled up by six longitudinal folds, consisting of a trans- 

 parent cuticle with a subjacent layer ; the cells of the salivary glands 

 may be seen, in section, to form one layer and two smaller complexes 

 below the oesophagus ; the secretion has an acid reaction. All the 

 thirty ca?ca are without a muscular investment, and consist only of a 

 thin fat-layer, a tunica propria, and an epithelium : the Malpighian 

 vessels are represented by two tubes, forming a loop, which are placed 

 near the median ventricle, and open not into the intestinal tract, but 

 into two sacs on the ventral surface of the animal. 



The genital organs of the two sexes are referable to a common plan, 

 consisting as they do of an unpaired germinal gland, semicircular in 

 form, lying freely in the body-cavity, and only surrounded by a rich 

 supply of tracheas ; there is connected with this gland a paired efferent 

 apparatus, which however becomes united into an unpaired piece, 

 and finally opens to the exterior in the median ventral line, between 

 the cephalothorax and the abdomen. Connected with the terminal 

 portion is a copulatory organ, into the anterior portion of which there 

 open a pair of accessory gland-organs ; the penis is rod-shaped, the 

 ovipositor is cylindrical, and the vagina has a seminal pouch on either 

 side. The testis is a simple tubular organ about 4 mm. long and 

 • 4 mm. wide ; the spermatozoa are large, biconvex, rounded cells, 

 with a lens-shaped nucleus ; the vasa efferentia commence as two fine 

 canals, and soon form a close coil ; the cells of the lumen become 

 commingled with the products of the testis ; the propulsion-organ has 

 a thick muscular layer, the fibres of which are transversely striated, 

 and there is a thick chitinous layer secreted by the epithelium ; the 

 lumen of the ductus ejaculatorius is narrow ; chitin is also to be found 

 in the penis. The ovary is horseshoe-shaped, invested by transverse 

 and longitudinal muscular fibres, and when mature is beset with a 



* Zeitschr. f. wiss. Zool., xxxvi. (1882) pp. 671-702 (2 pis.). 



