ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 23 



portion of the pedal aperture. All arc situated on the internal mantle 

 surface. Each is composed of a large number of individual glands em- 

 bedded in loose connective-tissue, and emptying their contents into the 

 mantle cavity by narrow efferent ducts. According to the nature of 

 the secretion, mucin-glands and luminous glands may be distinguished. 

 The mucin-glands produce a homogeneous mucus ; the others a fluid 

 secretion and a granular material. The cells are not used up in forming 

 the secretion, but what is exuded is replaced during a resting period 

 succeeding the emptying. The luminous secretion arises by a granular 

 transformation of the homogeneous content of the cavities of a coarse 

 meshwork. The innervation muscles and vascular supply of the 

 luminous organs are carefully described. 



The secretion expressed by the muscles is luminous when it touches 

 the water. It is extracellular as in Copepods and Ostracods. The 

 luminescence is not continuous ; it stops after continued stimulation, 

 and does not reappear until after a rest. It follows that the elaboration 

 of the luminescent material does not keep pace with the disassimilation. 



The luminescent material is made by living cells, but it is not living, 

 nor does it require a protoplasmic environment. It may be seen after 

 decomposition has set in. In normal circumstances the luminescent 

 material comes out in clouds from the opening of the siphon. With 

 low-power magnification it appears as if the animal were surrounded by 

 thousands of small stars. These consist of luminous granules within a 

 sheath of mucin, which isolates the essential material. 



Each luminous organ consists of three parts, the epithelium, a zone 

 where the luminous secretion undergoes transformation, and the glan- 

 dular tissue. Forster also gives a detailed account of the nervous 

 system. 



Arthropoda. 

 "■■ Insecta. 



Stylopization.* — Geoffrey Smith and A. H. Hamm have studied 

 the stylopization of a solitary bee, Andrena nii/rosenea, by Stylops melittse, 

 the adult female of which is a degenerate grub-like creature which 

 remains permanently inside the body of the bee. The male, before 

 hatching out as a winged insect, also develops inside the abdomen of 

 the bee, undergoing its larval stages and pupation in this situation. 

 The male pupa, in fact, closely resembles the adult female parasite, and 

 protudes a little cap between the segments of the bee's abdomen to the 

 exterior, which closely resembles the head of the female parasite which 

 is similarly protruded. When the adult winged male emerges from its 

 pupa and from the bee, it pushes off the protruded cap of the pupa and 

 leaves the old empty pupal case inside the abdomen of the bee, where 

 it can often be seen as a cavity opening to the exterior. 



From^a study of the structure and life-history of Stylops, it appears 

 that, despite the existence of active winged males, fertilization cannot 

 occur, and development is always parthenogenetic. The parasite obtains 

 its oxygen from the outside air by means of tracheal openings on the 



* Quart. Journ. Micr. Sci., lx. (1914) pp. 435-61 (4 pla.). 



