34 



DESCRIPTION OF THE PLATES. 



FIG. 12. The digestive apparatus of Tegenaria domestica, the common House Spider, after 

 Plateau, Bull. Acad. Roy. Belg. xliv, PI. I. Fig. 2. 



a. The anterior part of the cephalo-thorax, carrying the eight uni-corneal 



or mono-meniscous eyes arranged in two transverse rows. 



b. Second joint of the right pedipalp. 



c. Peduncle connecting the cephalo-thorax with the abdomen. 



d. The basal joints of the four pairs of ambulatory limbs. 



e. Two of the six spinning mammillae. 



f. The poison glands. Their ducts open on the terminal joint of the 



chelicerae (a, Fig. n). 



g. The anterior caecum of the cephalo-thoracic stomachal dilatation used 



in sucking up the juices of the prey. In front of it are the muscles 



of the pharynx ; behind it, the dilatator muscles of the stomach ; and 



at the sides it gives off, 



h. The caeca, eight in number, which enter the bases of the limbs and 



are recurved in the coxal joint. 

 i. The chylific or abdominal stomach receiving 

 j. The numerous ducts of the so-called liver or hepato-pancreas which 



secretes a digestive fluid. These ducts are numerous in Arachnida, 



and the glands large. 

 k. Caecum, opening on the dorsal side of the proctodaeum or rectum at 



the point where the ramified Malpighian tubules, shown as white 



lines in the figure, enter it. 



Fore-gut and digestive organs in Arachnida. MacLeod, Bull. Acad. Roy. 

 Belg. (3), viii. 1884. 



Structure and function of Liver. Bertkau, A. M. A. xxiii. 1884; xxiv. 1885. 

 Cf. Dahl, Z. A. viii. 1885. 



Anatomy of Epeira. Schimkewitsch, A. Sc. N. (6) xvii. 1884. Development. 

 Id. Z. A. vii. 1884. 



FIG. 1 2. Nauplius of Lepas fascicularis. Von Willemoes-Suhm, Ph. Tr., 1876, PI. X. Fig. 1 1. 



This Nauplius was taken in the Pacific Ocean during the passage of 

 H. M. S. Challenger from Japan to the Sandwich Islands. It is but just 

 hatched from the egg, and is still enveloped in a larval skin, destined to be 

 shed in a few hours. In size it measures about ^ of an inch. In subsequent 

 stages of the Nauplius form it grows immensely in size and acquires long 

 dorsal, caudal, and ventral spines. It was originally described by Dohrn 

 as Archizoaea gigas. 



a. The first uniramose appendage. It represents the first antenna, and 

 in the Cj//rw-stage f the Barnacle becomes four-jointed. The second 

 joint bears a suctorial disc, in the centre of which opens the duct of 

 the cement gland. By means of this apparatus, the 



