ON AMPHILINA PARAGONOPORA 69 



n short tilaineiit or ' tag ' (PL 4, tig. 30,/). Occasionally eggs 

 are shed into the uterus without a shell. Only unsegmented 

 eggs are to be found in a worm about 30 mm. long, and they are 

 situated in the portion of the uterus immediately adjacent to 

 the ovary, the rest of the uterus being empt}^. In an older 

 A . p a r a g n p o r a (a little over 40 ram. in length and cut 

 into serial horizontal sections) I have observed early segmenta- 

 tion stages — groups of four, eight, twelve and more blastomeres 

 — and in some of the early morulae it is possible to detect one 

 or two blastomeres which differ from the rest and which are 

 doubtless destined to form the investing membrane of the 

 embryo. In a worm a little over 70 mm. in length the uterus 

 is full of embryos, the oldest stage being a solid morula which 

 fills the shell, the morula being surrounded by an investing 

 membrane (PL 4, fig. 31 depicts a very young morula). In 

 another worm (87 mm. long when uncontracted, though it 

 shrank to 32 mm. when placed on a slide) which I cut into 

 serial transverse sections, the third limb of the uterus was full 

 of end^ryos of the stage represented by PL 4, fig. 34, while 

 earlier stages (e.g. that represented by PL 4, fig. 32, which I 

 drew on account of the single large internally situated blasto- 

 mere shown — gbl) were present in the other two limbs. The 

 embryos in limbs 2 and 3 of the uterus all possess a definite 

 ectoderm, while in limb 3 the embryos are further distinguished 

 (1) by the possession of a small group of large glandiform cells 

 (Ctc) which are drawn out towards one end of the embryo 

 and may be unicellular glands similar to those found in many 

 cerariae, and (2) by the elongation of the terminal cells at the 

 other end of the embryo (PL 4, fig. 33) and the secretion by 

 these cells of the ten (I think) calcareous booklets so charac- 

 teristic of the Amphilina larva (PL 4, fig. 34). PL 4, figs. 33 

 and 34 are drav/n from sections. In three worms each about 

 100 mm. long when uncontracted, the third limb of the uterus 

 was full of larvae still contained in their shells, which they 

 filled and were somewhat longer than the stage represented 

 by PL 4, fig. 34. At this stage the larvae are often liberated 

 and are about 100 microns in length. PL 4, fig. 35 represents 



