1904.] .sPoivrGKs OF the genus leucosolesia. 355 



spicules, not only in different specimens but even in any given 

 specimen. In order to separate the essential from the accidental 

 in tlie description of an Ascon, not only should many specimens 

 be studied, if possible, but in each specimen all possible forms of 

 spicules should be di-awn. One instance fi^om Haeckel's mono- 

 ,£;raph will suffice to illustrate this point. Under the genus 

 Ascandra {t. c. p. 81) the species botrys, which I have shown 

 below to be a synonym of hotryoides, is characterised as having 

 " triradiates obtuse-angled, rays 8 times as long as thick," while 

 the species nitida is distinguished from it by having " triradiates 

 right-angled, rays 4 times as long as thick." Now if tiie reader 

 will turn to my figures of the spicules of hotryoides given below 

 (text-figs. 97 & 98, pp. 388, 390), or, better still, will examine a spe- 

 cimen for himself, and compare the spicules with Haeckel's figures 

 of the triradiates of hotrys and nitida^, it will be found that in any 

 ^specimen the triradiates vary in slenderness from the types figured 

 by Haeckel for hotrys to those given for nitida, and that their 

 piiired angles vary from obtuse, in the more slender spicules, to 

 right angles in the thicker forms. There is therefore no argu- 

 ment to he drawn from HaeckeVs descriptions and figures against 

 putting these species together and considering hotrys and nitida 

 i\s synonyms of hotryoides. Whether they are really distinct or 

 not can only be determined by fresh investigation of the speci- 

 mens. Until that has lieen done we are justified in striking out 

 two of the three names. 



Another point in which variation occurs commonly is the re- 

 lative frequency of a giA^en type of spicule in different specimens. 

 Thus in some specimens a form of spicule may be abundant, which 

 in others may be so scarce that much seai'ching may be necessary 

 to find itt. As negative characters require much greater caution 

 to affirm than positive ones, it is only after very careful investi- 

 gation that one should declare a type of spicule to be absent in 

 any specimen which agrees in all other respects with other speci- 

 mens in which it is present ; even then it would be most unsafe 

 to separate such a specimen as a, distinct species on this character 

 alone. Yet it is in this Avay that Haeckel separated (in eiTor, as 

 it has pi'oved) the species hotryoides and complicata from their 

 synonyms hotrys and pinus. 



The extreme uncertainty and doubt which attach to all iden- 

 tifications of Ascon-species in works dealing with them, have, it 

 may be pointed out, one important consequence : that, namely, 

 of rendering utterly worthless all statements concerning theii- 

 geographical distribution. It is, indeed, my firm conviction that 

 the study of the distiibution of Ascons, perhaps of all Calcarea, 

 requires to be commenced de novo, and to be preceded by an accurate 

 study of their specific clia.racters. Until it is possible to liave 



* The extremely fanciful, if artistic, curves which Haeckel introduces into his 

 drawings of spicvdes mast be discounted in making comparisons. 



t Compare the very important observations of Topsent (Arch. Zool. Exp. (3) viii. 

 p. 43) on the different types of spiculation in Cliona celata at different ages. 



