469 



paragraph was abstracted, aud I find that the statements therein con- 

 tained are not altogether correct as regards the glands in connection with 

 the dorsal spines, while the opercular organs are not mentioned at all. 



From a number of preparations and sections, I find the following 

 arrangement of the poison-apparatus to obtain in T. vi p era, and I 

 have convinced myself that a precisely similar apparatus is present 

 in T. draco. 



To take first the opercular organ. The opercular spine is grooved 

 along both upper and under surfaces, and anteriorly, where it joins 

 the opercular bone, each groove ends in a conical cavity within the 

 latter. A large gland is present in connection with both dorsal and 

 ventral grooves: this consists of an expanded anterior lobe, the apex 

 of which extends into one of the bony cavities already mentioned, and 

 a narrower posterior portion , lying along the free part of the spine, 

 and passing insensibly into the anterior lobe. A short distance behind 

 the apex of the spine, each gland becomes continuous with the epi- 

 dermis, and the injection-apparatus has thus an arrangement somewhat 

 similar to that of a hypodermic syringe. 



The gland cells, which are arranged in some nine or te;n irregular 

 rows in the anterior lobe, and in three or four rows in the narrow 

 posterior part, are large and granular, and contain one or more dis- 

 tinct nuclei with nucleoli. In many of them, traces of recent division 

 are recognizable. 



The whole gland is enclosed in a delicate capsule, which is 

 surrounded by a mass of dermal connective tissue: no special muscles 

 are present in connection with it. The gland-cells, enclosed by the 

 capsule, extend into the grooves of the spine along its whole length. 

 Many of the cell-boundaries cannot clearly be made out, and from the 

 appearance of the cells I am inclined to think that, in the discharge 

 of their secretion, the cells simply burst, their contents finding their 

 way amongst the other cells along the grooves to the exterior. 



Owing to the toughness of the decalcified spines, and the looseness 

 of their connective-tissue sheaths towards their apices, I have been 

 unable to obtain thoroughly satisfactory sections throughout the region 

 where the cells of the epidermis and gland become continuous with 

 one another, and thus I am not quite clear as to the exact mode 

 in which the secretion passes to the exterior. But towards the termi- 

 nation of the gland, the dermal connective-tissue thins out, and the 

 epiilermic cells become involuted to as so become directly continuous 

 with the gland-cells. There can be little doubt, then, that the gland is 

 developed as a solid involution of the epidermis which does not show 



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