560 W, M. Bale: 



thread many times the length of the capsule, barbed, and coiled 

 round the longitudinal axis. Secondly, the small form, nearly 

 round, containing a short smooth thread, which forms a spiral oi 

 ■one coil only. Ihese two types are found in all the species. In 

 //. oil (/act IS (called by Jickeli //. vulgaris) is found a third sort, 

 consisting of an oblong or elliptic capsule, as long as the large 

 form, but much narrower, with a barbed thread which forms two 

 or three loose loops running lengthwise. H. vulgaris^ {H. grisea of 

 Jickeli) also has this type, and in addition a fourth form, of 

 medium size, with a barbed thread coiled about the longitudinal 

 axis. The last foim occurs in //. viridis also. According to 

 Jickeli's figures the large nematocysts of H. vulgaris much exceed 

 in size those of the other species figured by him. Brauer, in his 

 paper of 1908, describes his //. polf/pus (//. hraueri) as h,aving, 

 like //. vulgaris, four sorts of nematocysts, and remarks particu- 

 larly that the large form is much larger than the corresponding 

 form in H. oligactis. In H. oritntalis, according to Annandale, 

 there occurs occasionally a form intermediate in size between the 

 large and the small forms, but whether of the third or the fourth 

 type mentioned above is not stated. Von Lendenfeld says that 

 H. hexactinella has two sorts of cnidoblasts, with different cnido- 

 •cells. 



Brauer, in his paper of 1891, figures the eggs of the four 

 European species admitted by him. //. oligactis is there called 

 H. s/j. ?, //. vulgaris is called //. grisea, and the form now named 

 H. hraueri is called //. fusca. 



I am not aware of any observations on Australian Hydras 

 •covering the features which, according to the foregoing descrip- 

 tions, are necessary to be considered in discriminating the species. 

 All the brown hydras which I have seen agree in the so-called 

 ■" stalked " condition. When empty and fully extended the body 

 may attain quite an inch in length. Specimens which I collected 

 •at Williamstown many years ago, after being kept some time, 

 were found capable of extending the tentacles to three inches in 

 length; others found more recently at Kew did not display this 

 character during the short time they lived. The number of ten- 

 tacles varied between 5 and 8, but in the great majority of cases 

 there were six. I have not observed the eggs in any case. 



The character upon which von Lendenfeld founds his H. 

 hexactinella is unreliable, as tlie mere fact that a number of 

 -specimens from a single pool agreed in pnsse.ssinjr six tentacles 

 •cannot prove the invariability of the species in this respect. In a 



