128 



LECTURE VII. 



escapes from each ovicapsule, crawls off, becomes attached, and 

 developes its elongated stem and other characters of the Tubularia. 

 The process of development has been well observed by M. Van 

 Beneden* in another species of Tubularia (T. coronata Abildg.). 

 There are numerous clusters of ovicapsules in the same position as in 

 the T. indivisa. The capsules in each cluster are developed from 

 the sides of a short stem, and become more pedunculate as they are 

 situated nearer its extremity. The common nutrient cavity is con- 

 tinued into the stem, and sends off branches to enter the bases or 

 pedicles of the capsules. The germ-cell makes its appearance be- 

 tween the end of this canal and the summit of the capsule, as shown 

 in I, fig. 62,, which represents a young sessile ovicapsule detached 

 from the ovarian stem, showing the portion of the nutrient canal con- 

 tinued into it and the germ-cell below. The nutrient and respiratory 



currents are continued from 

 the general cavity of the 

 body through the ovarian ca- 

 nal and its diverticula which 

 enter the ovicapsules. The 

 germ-cell is thus supplied 

 with matter for its growth, 

 which proceeds rapidly by 

 the ordinary mode of multi- 

 plication of secondary germ- 

 cells by spontaneous fission. 

 As growth proceeds the ovi- 

 capsule expands, and the end 

 of the nutrient diverticulum 

 becomes surrounded by the 

 germ-mass, into the middle 

 of which the diverticulum 

 seems now to dip, as shown 

 in 2, fig. 62. The next 

 change is the development of a series of lobes which push aside the 

 diverticulum, as in 3: the lobes elongate into rudimentary tentacles, 

 and the base of the inner series of tentacles begins to appear, as at 

 b, 4 : this stage is better seen when the ovisac is viewed under pres- 

 sure as at 5. Where development has advanced thus far, the parietes 

 of the ovicapsule rupture and the embryo escapes, as a young polype, 

 with one series of tentacles, 6. It then becomes fixed, and begins 

 to develope its tubular body and its inner series of tentacles as in 7, 

 fig. 62. 



• CXI. p. 37. pi. i. 



Development of Tubularia coronata. 



