ON LAFffiA DlSPOlilANS SP. N. 107 



hydranth.s. The hydrorhiza on entering the hydrotheca grows 

 along the adcauline snrface and forms a sac (h. s.). From 

 the base of the sac there springs a hydranth which occupies 

 the remainder of the hydrotheca. It should be noticed that 

 the hydranth of the parasite is unprovided with a hydrotheca 

 of its own. 



In the case of the hydrotheca B the hydrorhiza-sac of the 

 parasite has continued its growth and has crept round the 

 margin of the mouth to the exterior, and has grown along the 

 outer surface of the host and produced a typical Lafcea-like 

 hydrotheca and hydranth {a). On emerging from the hydro- 

 theca of the host the hydrorhiza of the parasite provides 

 itself with a substantial perisarc (j). P.). 



A very similar history is shown in Text-fig. 2, which repre- 

 sents the second specimen. In this case it was a pinna that 

 was infested, while in the former case it was the main stem. 



The parasite started its growth at A and the hydrorhiza-sac 

 is seen on the adcauline surface of the hydrotheca, but there 

 was no polyp. Within the host the parasite has grown 

 upwards to the hydrotheca^ B, C and D. At C a polyp was not 

 formed or it had disappeared. At Z) the hydrorhiza-sac {h. s.) 

 has continued its growth and has passed through the opening 

 of the hydrotheca to the exterior, where it has forked into 

 two (_£/); .one branch has grown upwards and has produced 

 two typical hydrothecEe and polyps (a and h), and the other 

 has grown downwards and the growing apex ended at the 

 level of the line 5, 5. The downward-growing branch has, 

 foi' the sake of clearness, been omitted from the drawing, and 

 is represented cut off at E. This specimen is interesting in 

 that the polyps B, D of the parasite have shown some attempt 

 at forming their own hydrothecte, the hydrotheca of the host 

 being lengthened by a collar-like prolongation secreted by the 

 L a f oe a . 



The second specimen was carefully imbedded in paraffin 

 and cut into transverse sections, in order that the effect of 

 the parasite on the coenosarc of the host might be observed. 

 From the surface aspect it was not possible to discern whether 



