64 CTENOPHORA. 



from the point of the aboral processes of the body he "deutUch beobachtete, dass von hier sich baum- 

 artig verzweigte Gefasse gegen den Darmkanal erstrecken". If this proves to be correct, it is indeed 

 a most interesting feature, probably homologous to the proliferations from the meridional vessels of 

 Bathyctena Chuni (Moser). (Comp. p. 36, note). 



A verj' surprising feature of M. ovum is the strong development of its muscular system, as is 

 easily observed in the preserved specimens. (Comp. fig. 11). The infundibular canal is quite surrounded 

 by a thick layer of longitudinal muscles; at the level of the infundibulum they divide so as to pass 

 outside the diaphragm, continuing down along the outer side of the pharyngeal vessels (the inner side 

 of these vessels is close to the pharyngeal wall, not separated therefrom by a muscle layer). At the 

 level of the transverse, perradial vessels the longitudinal muscles must, evidently, be divided into four 

 groups, uniting again, two on each side, below the transverse vessel. It is only on sections, however, 

 that one can realize how exceptionally these mucsles are developed. As seen in fig. 12, representing a 

 transverse section of the infundibular canal, the muscles form a thick layer round the canal, the single 

 threads being arranged more or less distinctly in a feather-like way, as it is known e. g. in the earth- 

 worm. The single threads are rather thick, comma-shaped 

 ^^v in cross-section. The whole muscle-bitndle appears to be 



'tv'vt-^N* 'ifAPW '''i,'f'''Ci^-- limited outwards by a fine membrane. The longitudinal 



'',;-';-t\ , muscles along the outer side of the pharyngeal vessels 



'" ■ • '.^^^ are arranged in a similar way, but the muscle threads 



, . .' M' ','■';,'."', ^-N^-^^y are less numerous here. Between the pharynx and the 



'■ " ^ -' ' tentacle-bases there is a conspicuous network of anasto- 



Fig. 12. Transverse section of the infundibular canal mosing muscle-strands. Also these smaller bundles appear 



oi Mertensia ovum. inf. c. infundibular canal; 1. m. Ion- . ,. , , i 1 1 ,1 • 1 rr~-\ 



.. J- , , J- 1 , „, m sections to be surrounded by a thm membrane. Ihe 



gitudinal muscles; r. m. radial muscles. 90/1. ■' 



same reticulum of muscle-bundles is also seen in the 

 aboral part of the animal, taking almost the appearance of ring-muscles over the muscle-bundle round 

 the infundibular canal; in fact, I am not quite sure whether there are not real ring-muscles here. 



This strong development of the musculature is quite astonishing and, as far as hitherto known, 

 quite unique in the Ctenophores. It would, indeed, be very interesting to have this species made the 

 object of a close histological and anatomical study. It may be supposed that its nervous system will 

 prove to be considerably more developed than usual among Ctenophores, judging from its muscular 

 system. 



The very interesting observation of Mertens, that it uses its tentacles for attaching itself to 

 stones etc. on the bottom, when the sea is in motion through stormy weather, in order to avoid being 

 thrown ashore and crushed, may be recalled here. Likewise Mertens (p. 527) records it to possess 

 strong regenerative power. (Comp. below, sub. Bolina iji/zmdibulum). 



Several specimens were taken by the "Ingolf at the stations 29 (65° 34' N. 54° 31' W.), 

 33 (67°57'N. 55° 30' W.) and 34 (65° 17' N. 54°i7'W.); in the Journal of the Expedition it is ment- 

 ioned from station 32 (66° 35' N. 56° 38' W.), all these stations being in the Davis Strait. — On the 

 "Danmark" Expedition it was observed by Mr. Fr. Johansen in considerable numbers in the months 

 of August and September 1907 at "Danmarks Havn" (North-East Greenland, 76° 47' N. 18° 45' W.), the 



