ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 433 



wall, and thence a branch goes into the ccelom, extends to the enteron, 

 where its wall fuses with that of the gut. There are also schizocoel 

 spaces in the arms, which fuse around the pharynx into an oral schizocoel- 

 sinus; in these the central nervous system is suspended. On this 

 latter there is a blood-vessel, placed in a poorly developed connective- 

 tissue-septum. These radial blood-lacunae also form a circumoral ring, 

 whence there is a communication of blood to the so-called heart. 



Ccelenterata. 



New Method of Multiplication in Hydroids* — Prof. W. K. Brooks 

 has observed a new method of multiplication in a species of Oceania 

 found at the Bahamas. The hydroid larva is a small Canipanularian, 

 and the hydranths are carried in toothed cups ; the blastostyles spring 

 from the root, inclosed in nearly sessile gonothecae, and produce a series 

 of medusa-buds, which mature and escape in succession from the 

 distal end. Soon after it is set free the medusa has a shallow bell, 

 four radial and four iuterradial tentacles, capable of considerable exten- 

 sion, an otocyst on either side of the base of every interradial tentacle, 

 and four rudimentary reproductive organs. A few of these medusae 

 presented a remarkable and unexampled peculiarity, for they had true 

 blastostyles growing out from their reproductive organs into the cavity 

 of the bell ; these were inclosed in chitinous gonothecae, covered with 

 medusa-buds exactly like those on the blastostyles of the hydroid com- 

 munities, and the little medusa which escaped from them was identical 

 with those which were reared from the hydroid blastostyles. As the 

 homology between blastostyles and hydranths is undoubted, and as 

 nobody has questioned Prof. Brooks's dictum that the hydra is essentially 

 a medusa-larva, we have in this Oceania an adult which buds off larvae. 



Sections show that the relation between the medusa and the blasto- 

 style is quite anomalous and very different from that which ordinarily 

 obtains between the bud and the parent in the Hydromedusae. All the 

 medusae with blastostyles which were examined were found to be males, 

 with a well-defined layer of ectoderm outside the unspecialized germ- 

 cells of the reproductive organ, and this layer is directly continuous 

 with the ectoderm of the blastostyles, but there is no connection 

 between the radiating canal of the medusa and the stomach of the 

 blastostyle, nor is the endoderm of the latter an outgrowth from that of 

 the medusa. The endoderm of each blastostyle is quite independent 

 of the same layer in other blastostyles upon the same reproductive 

 organ. 



Near the proximal end of each blastostyle the ectoderm becomes 

 thickened to form a glandular collar, by which the perisarc of the gono- 

 theca is excreted. The layer of ectoderm bends round the base of the 

 sheath of perisarc, folding it into a circular furrow, outside which the 

 ectoderm and its supporting layer is directly continuous with that of 

 the medusa. The endoderm is continued into the substance of the 

 reproductive organ as a hollow tube, which divides up into smaller 

 tubes ; these ultimately split along one side and flatten out into a single 

 layer of cells directly continuous with the unspecialized germ-cells of 

 the reproductive organs. In the body of the blastostyle the endoderm 

 cells are opaque, granular, vacuolated, and filled with food-particles, 



* Johns-Hopkins Univ. Circulars, vii. (1888) pp. 29-30. 

 1888. 2 H 



