waite: antennal glands in iiomarus americanus. 157 



The paraffin method of embedding has been used exclusively. The 

 cuticular shell in the larval stages is rather resistant, and soon dulls the 

 knife, but with a sharp knife good series 6§ micra in thickness were 

 obtained. 



I. Structure in the Adult. 



The structure of the adult antennal gland in the genus Homarus has 

 been described by only one writer, Marchal ('92, pp. 15G-1G3, Plate Vll. 

 Fig. 1), who gives an account of the organ in H. vulgaris. There is no 

 published account of this gland in H. americanus except a short abstract 

 of this paper (Waite, '98). 



A. Gross Anatomy. 



The gland, with its accessory structures, is situated at the base of the 

 second antenna, and the most of it is within the cephalothorax. It 

 occupies the greater part of the space beneath, and on the side of the 

 masticatory stomach, anterior to the voluminous hepato-pancreas. The 

 organ as a whole may be divided roughly into three parts, which are 

 easily recognized and sharply separated, namely: (1) the gland proper, 

 often referred to hereafter simply as the gland ; (2) the overlying 

 vesicle, or storage reservoir; and (3) the duct leading to the exterior, 

 together with the tubercle upon which it opens. 



The gland proper lies almost entirely on the ventral floor of the cephalo- 

 thorax, but its anterior median lobe extends into the base of the antenna. 

 It lies close to the sagittal plane, the median edges of the two glands 

 being but about five millimetres apart. ^ None of the principal axes of 

 the gland proper are parallel to the principal axes of the body. The 

 dorsal face is so inclined to the frontal plane of the animal that its 

 anterior edge is 20° or 30° more dorsal than its posterior edge, and its 

 lateral border 25° or 30° more dorsal than its median. The chief axis 

 of the gland as viewed from above runs from the anterior notch or hilus 

 to the most distant point of the posterior edge (Plate 1, Fig. 1). This 

 axis makes an angle of about 30° with the sagittal plane of the animal, 

 its anterior end being nearer that plane. 



The general shape of the gland proper as seen from above resembles 

 that of a cordate leaf with a blunt point, the notch being anterior (Plate 1, 

 Fig. 1). The dorsal face is irregularly concave. This concavity is filled 



1 All measurements given for the adult gland are for an average adult nine 

 inches {— 23 cm.) in length from tip of rostrum to tip of telson. 



