Fig. 4. a. End-to-end apposition of muscle fibers in the epidermis of 

 Pelmatohydra. Note the irregular line of contact and the increased density 

 associated with the two cell surfaces (arrows). The myofilaments appear as 

 small streaks oriented towards the attachment zone. The subjacent mesoglea 

 exhibits very fine filaments more or less randomly arranged, b. End-to-end 

 apposition of gastrodermal muscle fibers at high magnification. The fila- 

 ments in gastrodermal muscle appear less conspicuous than those in the epi- 

 dermis. M, mitochondrion; ME, mesoglea. a — 17,000X. b — 80,000X. 



57 



