7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 45 



alternate with shorter sterile mesenteries, but usually gonads (which are her- 

 maphrodite) are found only on the 3rd and 5th and exceptionally on the 7th; 

 in one specimen gonads were present on the 4th. The 3rd mesenteries are 

 the longest and almost reach the aboral pole. The free edges of the mesen- 

 teries are thickened, but free mesenterial filaments, hanging into the coelenteron, 

 are found only at the aboral end of the 3rd (and sometimes the 5th) mesen- 

 teries, i.e. near the aboral pore, through which they have been seen protruded. 

 The ectoderm of this filament is chiefly composed of glandular elements but 

 nematocysts also occur, the endoderm is formed of flagellated cells among which 

 sexual cells are sometimes seen; the mesogloea forms a flattened axis. The 

 ova, when ripe, have a striated envelope; they may issue through the aboral 

 pore or the stomodseum. The aboral pore may be very large. A specimen 

 multiplied by spontaneous fission, in others artificially divided near the middle 

 of the column, the two parts soon became indistinguishable from ordinary spe- 

 cimens. This experiment succeeded equally well with C. solitarius. 



Carlgren( 1 ), working on Metridium dianthus and Sagartia viduata, finds that 

 only pieces which contain a portion of the pedal disc can reproduce a com- 

 plete anemone. Pieces of S. with a part of the outer region of the oral disc 

 can form a stomodseum, pieces of the body wall may produce tentacles. The 

 distal part of a transversely cut M. cannot form a pedal disc. Heteromor- 

 phosis is rare in M. Lateral cuts, not too deep, in the distal part of M. 

 generally heal; when they reach the stomodseum little heads (Kopfchen) are 

 formed, each with tentacles, mouth, and stomodseum communicating with the 

 old one. A lateral cut, not involving the stomodseum, caused the formation 

 of a small head with typical tentacles and oral disc but no mouth or stomo- 

 dseum. Polarity is clearly marked in S. In pieces in which a portion of 

 the pedal disc and of the body wall are connected with each other only by 

 mesenteries, there appear on the oral, rarely on the aboral, cut surface small 

 heads with tentacles, mouth, stomodseum, siphonoglyph and a formative 

 zone for mesenteries. This was also the case in similar pieces of M. In 

 some cases there were, on the pieces, two zones of growth, with the new 

 directive plane more or less at right angles to the original radii. 

 Regeneration in very small laceration-pieces of S. progressed somewhat as 

 in similar pieces with 8-16 mesenteries [see Bericht for 1904 Coel. p 26]. 

 In a few cases the mesenteries arose biradially, with the new directive 

 plane at right angles to the median plane of the piece; possibly such pieces 

 arose by coalescence of two pieces. The form of small laceration pieces is 

 an insignificant factor because they soon round themselves off. Pieces which 

 are deeply cut out of the oral side may give rise to Doppelbildungen. Small 

 pieces which contain directive mesenteries often form double animals, there 

 being a stomodseum on each directive mesentery. In a few cases no formative 

 zone for mesenteries was produced. The behaviour of the directives is very 

 variable in the pieces. The regulation of small pieces of M., without direc- 

 tives, follows the same course as in S. A pair of the old mesenteries is asso- 

 ciated with the stomodseum while mesenteries are being formed in the growth 

 zone. Generally the mesenteries develop biradially, they never arise in the 

 formative zone according to the bilateral type with 3 pairs of mesenteries. 

 The monoglyphic form arises in M. from pieces without directives, the diglyphic 

 form from those which have a pair of the old directives, but there may arise, 

 in M. and 5., diglyphic forms from pieces of the pedal disc without directives. 

 Pieces of the pedal disc of M. and S. can grow to complete animals but re- 

 generation is slower than in laceration-pieces. The cut edges join, and the 



Zool. Jahresbericht. 190'J. Coelenterata. 



