Holocrine

Holocrine (sebaceous) Ventral gland Mongolian gerbil, Meriones unguiculatus... 

Although secretions from the (so-called) penetration glands undoubtedly play a role in penetration, their nature and function are largely unknown. The glands have been particularly studied in H. diminuta and H. nana (205, 888, 889). In most species, glands have been described as syncytial (Fig. 8.16) or multicellular, but in H. nana they appear to be unicellular (205). One or two pairs of ducts may be present and these are supported by microtubules. Secretion has been described as being holocrine in some species (as in trematode miracidia and cercariae) but apocrine and merocrine secretory mechanisms have also been proposed for others (205, 242, 443). 

Albone, E. S., 1984, "Mammalian Semiochemistry the Investigation of Chemical Signals Between Mammals," J. Wiley and Sons, New York. Alexander, S. A., and Maderson, P. F. A., 1972, Further observations on holocrine epidermal specializations in iguanid lizards. Am. Zool., 12 731. 

Maderson, P. F. A., 1972c, The structure and evolution of holocrine epidermal glands in sphaerodactyline and eublepharine gekkonid lizards,... 

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