10 ARKIV FÖR ZOOLOGI. BAND 8. NIO 18. 



by the coalescence of the neural spines and the pterygio- 

 phores. The posterior six portions insert into the dorsal 

 rays of the caudal fin. The tendons going to the dorsal fin 

 pass through canals formed by grooves in the large cartila- 

 ginous piece which represents the coalesced tips of the ptery- 

 giophores. These grooves are laterally bounded by the härd 

 corium, so that true canals are formed (Fig. 10). The ten- 

 dons to the caudal fin run through canals in the härd corium. 



The ventral mäss of muscles has a similar structure. To 

 the anal fin 17 tendons are attached, to the first ray the 

 first and second tendons, to the second ray the third and 

 fourth tendons. Into the ventral rays of the caudal fin 7 

 tendons are inserted. 



Exteriorly to these muscles for the dorsal, caudal and 

 anal fins no muscles are present in adult specimens. The 

 wall of the body-cavity shows on each side only two areas 

 of muscle-fibres. One consists of fibres, which originate from 

 the body wall and run cranio-ventrally inserting into the 

 pectoral arch. Some other fibres originate from the body 

 wall and are inserted into the body wall at about the point 

 where the pectoral fin inserts. These fibres pass cranio- 

 dorsally. 



A very small paired muscle runs from the posterior part 

 of the head to the first pterygiop höres. The two muscles are 

 almost connected with each other. 



Which is the morphological nature of these body-muscles 

 present in Mola? The only author who has tried to answer 

 this question is, as far as I know, Meckel. He writes (p. 79): 

 »Man sieht also, dass hier alle, gewöhnlich getrennten Muskeln 

 unter einander verschmolzen und dass entweder der hintere 

 Theil der Seitenmuskeln verschwand und durch die sehr ver- 

 grösserten Seitwärtswender der Flosse ersetzt wurde öder, 

 wahrscheinlich richtiger, ihre Gestalt und Richtung annahmen. 

 Dagegen sind die Muskeln der Afterflosse ihrer Gestalt, Lage 

 und ihrem Ursprunge nach, wahrscheinlich die gewöhnlichen 

 eignen Muskeln derselben.» About the muscle which is 

 inserted in the pectoral arch I think there can be no doubt 

 that it corresponds to a portion of m. obliquus injerior. The 

 greater part has quite disappeared. The other muscle pre- 

 sent in the wall of the body cavity has the fibres arranged 

 in the same direction as m. obliquus superior. That it repre- 



