90 



HYDEOZOA. 



The communication by means of transverse canals is another arrange- 

 ment exactly similar to what exists in the adult Beroeform Medusae. 



Fig. 43. 



Development of Tubularia by free gemmse. 



(208.) The outer membrane presents eight longitudinal canals (fig. 

 43, G, H, b), which are found to be filled with cellules, but in which no 

 movement has been observed. It is to the presence of these longitu- 

 dinal bands that the embryo in this stage of its development owes its 

 resemblance to certain fruits, more particularly to a melon. 



(209.) From the anterior part proceed four appendages (fig. 43, G, d), 

 which were still undeveloped at the period of the detachment of the 

 young polyp, but now insensibly unfold themselves. These are the 

 tentacula. In the centre there projects a rounded opake body, gene- 

 rally of a red or yellowish tinge, which is the stomach. This viscus 

 communicates, as has been stated above, with the four longitudinal 

 vessels, and is the only opake part of the embryo. It opens in front 

 by an orifice that constitutes the mouth ; the whole organ is emi- 

 nently contractile, turning in all directions like the body of a Hydra, 

 sometimes elongating itself like a worm, and at others shrinking so as 

 to be almost imperceptible. 



(210.) If the embryos examined in this condition be vigorous, their 

 movements are very varied, and the forms that they assume extremely 

 singular. The regular contractions above noticed are the most simple 

 actions ; the two poles separate and approach each other alternately, 

 whence results the progression of the little creature. But this con- 

 traction may be -carried to a still higher degree : the rounded stomach 

 in the middle of the embryo not only moves itself about in every direc- 

 tion, but it seems to make efforts in the middle of its transparent 



