472 ME. B. T. BROWNE ON [Mar. 17, 



belongs to the Gymnoblastic group of Hydroids. The Medusoid 

 Willia stelluta has been always considered a Leptomedusa and 

 was placed by ITaeckel among the Cannotidse. As I did not know of 

 any clearly proved case of a gymnoblastic hydroid having a medusa 

 which must be classified with the Leptomediisse, I examined by 

 means of sections the exact positions of the gonads. It is one of 

 the chai'acteristic features of the Anthomedusse to have the 

 reproductive cells on the wall of the stomach, and of the Lepto- 

 medusiB to have the reproductive cells upon the radial canals. 



When I first sa\\' Willia I certainly regarded it as a Lepto- 

 medusa. At the base of the stomach six broad canals are given 

 off ; these run along a short peduncle and over the top of the 

 sub-umbrella ; along this portion the gonads are situated ; at the 

 point where the gonads terminate the canals suddenly decrease in 

 diameter and become somewhat inconspicuous. The question arose 

 whether to consider the broad part of the canal upon which the 

 gonads are situated as a prolongation of the stomach or as a part 

 of the radial canal itself. To determine this point, I cut several 

 series of sections of medusas belonging to the second and third 

 stages. All the sections clearly show that, the endoderm-cells of the 

 stomach are continued, without any change in size or shape, along 

 the whole length of that portion of the canal upon which the gonads 

 are situated. At the point where reproductive cells terminate the 

 canal suddenly decreases in diameter, and the endoderm-cells 

 become very small and flat. I think that portion of the canal 

 upon which the gonads are situated may reasonably be regarded as 

 a prolongation or lobe of the stomach, and that the true radial 

 canal commences at the end of this lobe. 



The sections also show reproductive cells at the base of the 

 stomach itself, before it branches into the six lobes. 



I think this medusa is as interesting as the hydroid is remark- 

 able. It shows a kind of transitional stage between the Antho- 

 medusae and Leptomedusse. The continuation of the endoderm- 

 cells, without change, into the lobes, and also the continuation of 

 the reproductive cells from the base of. the stomach itself along the 

 lobes, strongly point to Willia belonging to Anthomedusas, and not 

 to the Leptomedusae. 



Disthibution : — 

 Hydroid Form. 



England — Ilfracombe, Ilinclcs *, 

 Medusoid Form. 



Scotland — St. Andrews, Mcintosh. Oban, Forhes. 



England — Plymouth, Oarstang and E. T. B. Fowey, Peach. 

 Falmouth, Cocks. Penzance, Forbes. Ilfracombe, Oosse. 



Ireland — Valencia Island, E. T. B. 



