1904.] SPONGES OF THE GENUS LE17C0SOLENIA. S57 



range of variations shown Ijy the spicules in every specimen. It 

 is, moi'eover, exti-emely easy to ovei-look inconspicuous forms of 

 spicules. It was not until I had studied carefully many specimens 

 of hotryoides and variabilis that I became aware of the invariable 

 pi-esence in both of slender straioiit barbed monaxons (text-fig. 

 94, fig. 10 k, I, p. 377; text-fig. 97,'' fig. 22 I, u, &c., p. 388). 



For the study of the species dealt with in the present memoir 

 I have examined specimens from various sources. Besides those 

 which I have collected myself at Plymouth, Roscoff, and elsewhere, 

 or which have been sent me by friends, I have had access to 

 specimens of historic impoi^tance in the private collection of 

 Canon A. M. Norman, and in the collections of the British 

 Museum and the Bei'lin Museum. Among those who have given 

 me specimens my thanks are especially due to Mr. Walter 

 l^ai'stang, who sent me numerous specimens from the neighbour- 

 hood of Plymouth, and Monsieur E. Topsent, who sent me 

 specimens from Finance. Canon Xorman, with great liberality, 

 placed his collection at my disposal and allowed me to examine 

 all his specimens*. The information I acquired in this Avay was 

 most valuable, since his collection compiised type specimens of 

 Bowei'bank and others, as well as many which had been thi'ough 

 Haeckel's hands, identified by him, and returned with the labels 

 written or endorsed by Haeckel with his own hand. Not less 

 valuable, and more numerous, were the specimens in the British 

 Museum of Natural Histoiy, for access to which I have to thank 

 Dr. A. C. L. Giinther, F.R.S., who permitted me to examine all 

 the specimens, and Mr. Kirkpatrick, who most kindly looked 

 them out for me and instructed me as to the various handwritings 

 on the labels. For examination of the specimens in the Bei-lin- 

 Museum I am indebted to Di". Weltner, who, by the kind per- 

 mission of Professor Moebius, was so good as to send me small 

 pieces of the Ascons in the Beilin collection, to enable me to study 

 their spiculation. 



A list of the specimens from various sources which I have thus 

 been able to examine is given below, following the descriptions of 

 the species, fi-om which it will be seen that my identification of a 

 specimen is often very different from that of its previous label. 

 I have only to add that, in the case of each specimen mentioned, 

 the spicules have been carefully drawn by me with the aid of the 

 camera lucida in the manner described above. The illustrations to 

 this memoir are tracings from a selection of the drawings so 

 made. 



IV, General Remarks on the Characters op the 

 Species of Leucosolenia. 



The external form and mode of growth in the genus Leucosolenrta 



* It is uow ten years since 1 examined Canon Norman's specimens, and nearty as 

 long since I obtained for study the specimens from the British and Berlin Museums. 

 Much stress of other work has prevented the completion of these investigations. 



