GLANDS. 



179 



an ectodermal invagination, while Kingsley (No. 55) has proved 

 that, in Crangon, it arises from a collection of mesoderm-cells, and 

 only secondarily does the vesicle open externally. The mesodermal 

 origin of the shell-gland has been established in the case of the 

 Cladocera by Grobben (No. 11) and Lebedinsky (No. 11a). 



A ^/^ 



-SO 



Fig. 8S. — Three transverse sections through 

 young Branchipus larvae (after Claus). 

 A, transverse sections through a thoracic 

 segment at the Metanauplius stage. B, the 

 same through a thoracic segment at a later 

 stage. C, the same through an abdominal 

 segment at a still later stage, c, cardio- 

 blasts ; d, intestinal canal ; dl, dorsal 

 longitudinal muscle ; g, rudiment of the 

 ventral chain of ganglia ; h, cardiac cavity ; 

 01', ovary ; s, pericardial septum ; so, 

 somatic, and sp, splanchnic layers of the 

 mesoderm ; li, ventral longitudinal muscle. 



Our belief that these two glands, which formerly were often confused with 

 one another, are the homologiies of the Annelidan segmental organs, rests 

 partly on the statements of Leydig and Gegenbaur. This interpretation 

 of the antennal gland is supported chiefly by the careful anatomical researches 

 of Grobbex, and by the agreement thereby revealed between the structure of 

 this organ and the nephridia of Peripatus, so thoroughly investigated by 

 Sedgwick. According to Grobben, we must distinguish in the antennal 

 gland (in the Entomostracan larva as well as in the adult Malacostracan) two 

 sections — an "end-sac" and a much-coiled tubular portion which often enlarges 

 before opening on the basal joint of the second antenna into a vesicle (urinary 

 bladder). All these separate parts of the gland may become more complicated 

 by the development of secondary diverticula. In recent researches, in which 

 the indigo -carmine injections recommended by Kowalevsky were used, 

 Weldon (Xo. 68),* working on Palacmon serratus, concluded that the structure 



* Cf. Maechal, Compt. Rend., Tom. ex., cxi., and Weldon, Quart. Journ. 

 Micro. Sci., Vol. xxxii. 



