FISHERY BULLETIN, VOL. 71, NO. 4 



with CBE-lactic acid), frequently confirmed the 

 connection between the pore and a single, gland- 

 like, spherical to ovoid sac. roughly 30 to TSjLt 

 across the maximum dimension (Figure 2b), 

 and not unlike the glands noted in other cope- 

 pods (Fahrenbach, 1962; Clarke et al., 1962; 

 Park, 1966). Integumental glands may occur 

 on all the segments of the body (Figure 3). 



A notable feature of the perforations (both 

 sensilla and gland duct types) is their relation- 

 ship to formation of the integument. Resembling 

 that described in other arthropods (Dennell, 

 1960), the exoskeleton in Encalanus has been 

 observed in the present .study to consist of prisms 

 apparently laid down over individual cells of 

 the hypodermis. The prisms are joined by inter- 

 prismatic septa presumably of secreted pro- 

 cuticle that stains darker with CBE than the 

 prisms. The organ-forming and neural cell 

 extensions pass between cells of the hypodermis. 

 Hence passage of these features through the 

 integument occurs in the interprismatic septa, 

 a feature frequently observed in this study in 

 all of the species. In specimens with well dif- 

 ferentiated prisms, numerous minute perfora- 

 tions formed by the pore canals (-0.1 to 0.3yu) 

 may be seen within each prism. As Dennell 

 (1960, p. 461) states, perforations observed on 

 the surface of the cuticle formed by integumental 

 organs and pore canals cannot be confused; 

 the latter are numerous, minute, and within 

 the margins of individual prisms; the former 

 are an order of magnitude larger and lie in the 

 septa between prisms. Pore canals were not 

 considered in the analysis of Eucala)iHS perfora- 

 tions. 



LIMITATIONS 



Failure to obtain total elimination of tissue 

 and precipitates in the hot alkali treatment and 

 insufficient staining were the commonest sources 

 of difficulties in carrying out microscopic exami- 

 nation of the perforations. Specimens that had 

 moulted shortly before fixation and species in 

 which the exoskeleton is relatively flabby (e.g., 

 species of the elongatus group) require greater 

 care in staining and handling. 



Occasionally, areas of perforation size fail 

 to take up as much stain as the surrounding 



Figure 2. — Appearance of intact integumental organs and 

 the perforations left by these organs in the integument of 

 KOH-treated specimens of Encalanus subtemiis (adult 

 females). Specimens prepared for scanning electron micro- 

 scope by Freon critical-point drying, vacuum coating 

 with gold-palladium and examined with the aid of a 

 Cambridge Stereoscan S.E.M. a. entire specimen in dorsal 

 view; 1 mm = 24.4 ju. b. schematic sectional view of typical 

 combination of peg (basiconicum) sensillum and inte- 

 gumental gland with pore. c. thorax in dorsal view; 1 mm 

 - 8.5 ;n. d. hair (trichodeum) sensillum; 1 mm = 1 n- 

 e. perforation in integument left by hair sensillum in KOH- 

 treated specimen; 1 mm = 0.25 n. f. pore of integumental 

 gland; 1 mm = 0.25 ju. g. typical arrangement of peg 

 sensillum (right) and pore (left), h. perforations in integu- 

 ment left by peg sensillum (right) and pore (left) in KOH- 

 treated specimen, i. pit (coeloconicum) sensillum (left) 

 and pore (right) of integumental gland, j. perforations in 

 integument left by pit sensillum (left) and pore (right) in 



974 



