181 J. FULLAGAR ON TUBIC'OLARIA NAJAS. 



when I returned, that which I had been anxiously looking for, had 

 taken place during my absence, and neither egg nor young animal 

 was to be seen. This somewhat puzzled me, as I expected at least 

 to see an empty and deserted shell, but nothing of the kind was to 

 be found. The egg continues to hold its form, as shown at Fig. 3, 

 to the last, when the motion within increases in violence, evidently 

 the creature is struggling to escape from its prison ; I now expected 

 to see the egg open and the animal escape, leaving the empty shell 

 behind, but this was not the case, for after some more violent turn- 

 ings and twistings the whole egg itself elongated, and took the form 

 of Fig. 5 ; thus, the outer case of the egg now became the outer 

 skin of the animal, and for about the space of ten minutes continued 

 to turn and twist in all directions, sometimes elongating itself to 

 twice the length of the original egg shape, and then again contract- 

 ing, but still remaining in the place it had occupied, as shown at 

 Fig. 1 i ; at the end of about ten minutes it suddenly evolved a cir- 

 clet of cilia (Fig. 5 o), and quickly assumed the form of Fig. 6 ; it 

 then immediately commenced to move up towards the head of the 

 parent, and on coming in contact with its cilia (Fig. 1 p), it sheered 

 off into the water, and swam quickly away, as though rejoicing in 

 the new life just acquired ; and thus for a time it roams about at 

 large. This continues for a short period, when it chooses a spot and 

 settles down, fixing itself by its posterior end to some weed (Fig. 7), 

 with one circlet of cilia in rapid motion on the margin of its head, 

 the head being raised on a sort of neck. At this stage the internal 

 arrangement of the stomachs, &c, are seen to be very similar to 

 those of the adults (Fig. 7 r). In the course of two days the wreath 

 of cilia appears to be divided, occupying two projections on the head, 

 and having then the appearance of two rotating wheels, very much 

 resembling those of Rotifer vulgaris; this continues for a time, when 

 it is gradually changed to the form shown in Fig. 8, and the two 

 lobes become further expanded ; thus the gradual growth goes on 

 until the full form of the adult is attained. At times the young 

 creature closes itself up in the form of Fig. 9, and now the gela- 

 tinous tube begins to form (Fig. 8 s.) It is not clear to me where 

 that comes from, but 1 think it probable that it is thrown out from 

 the body, thus forming the tube into which the Najas retires sud- 

 denly when alarmed ; and this it frequently does without in any 

 way interfering with the eggs, though the Najas goes down to, and 

 even passes the eggs when it retires, and sometimes two and three 



