7^ 



in strong contrast with the surface of those species of Sar- 

 cophytum and Lobophytum I have examined, in which it is 

 relatively smooth. It is very difficult in this genus to 

 determine accurately the number of autozooids and siphono- 

 zooids in a given area as it is impossible to distinguish except 

 in series of sections the young retracted autozooids from 

 siphonozooids. The relative number of the two forms seems 

 to vary in different parts of the colony, the siphonozooids 

 being apparently more numerous near the apex than in the 

 neighbourhood of the stalk. At a distance of 30 mm. from 

 the apex I counted in an area of i sq. cm. 12 autozooids, and 

 36 siphonozooids, and in another f sq. cm., 90 mm. from the 

 apex, I counted only 5 autozooids and 13 siphonozooids. The 

 arrangement of the polyps is, however, very irregular, the 

 number in any given area depending very largely upon the 

 condition in which the part was when the colony was killed. 

 The only point as regards the arrangement of the polyp that 

 can be used for systematic purposes is that the siphonozooids 

 are relatively fewer than in the genera Sarcophytum and 

 Lobophytum. We have not yet any very satisfactory state- 

 ments of the average number of siphonozooids in these 

 genera. In my sections, however, I find in a species of 

 Lobophytum collected by Dr. Willey more than 40 siphono- 

 zooids to each autozooid ; and, judging from the descriptions 

 of Moseley, as well as from my own sections of the genus 

 Sarcophytum, there must be in some parts of the colony at 

 least as many as 25 siphonozooids to each autozooid. In 

 Acrophytum there are rarely more than 4 or 5 siphonozooids 

 to each autozooid. 



The spicules of Acrophytum are found in a dense row in 

 the superficial ectoderm of the coenenchym. They are very 

 characteristically club-shaped (see Plate IV., B'), 0.25 mm, 

 long by 0.1 mm. broad. Below the surface the coenenchym 

 is almost entirely free from spicules, a very striking feature of 

 the genus (or species ?) when it is compared with the two 

 other dimorphic genera previously mentioned. There are no 

 spicules in the exsert portion of the polyps. 



Sex : The larger of the two forms is a female, the large 

 brown eggs occurring in small numbers in the autozooid 

 polyp tubes. They vary very considerably in size, the largest 

 being oval in shape and nearly 2 mm. in greatest diameter. 

 Judging from the character of the germinal vesicle, I am of 

 opinion that the larger eggs are ready to be spawned , or, in 

 other w^ords, the specimen was sexually mature. The eggs 

 of this species are the largest I have observed in any Alcyon- 



