646 



SCIENCE. 



[N. S. Vol. I. No. 24. 



a ring is formed by a number of subcartila- 

 ginous segments, wliicli give rise to as manj^ 

 processes for the support of cii'ri just before 

 their posterior ends, which connect with 

 tlie succeeding segments. A specialized 

 heart is also wanting, and so likewise are 

 paired eyes, as well as auditory and olfac- 

 tory organs. The sense of sight or light is 

 subserved imperfectly by a median ' eye 

 spot ' sessile on the forward end of the 

 nerve tube between the foremost pair of 

 nerves. Immediately behind the eye spot 

 is ' a small pit in the " body-wall, reaching 

 from the outer surface of the bodj^ to the 

 anterior wall of the brain. This is known 

 as Kolliker's olfactory pit, after its discov- 

 erer' (p. 19). Everj^ other feature of the 

 organization of the animals in question is 

 noteworthy, and Mr. Willey tells about 

 them in detail in the work which is here 

 noticed, and to that reference may be made 

 for further information. 



The species of Lancelets are few; only 

 nine or ten at most are known. Thej' are 

 of small size, ranging from about half an 

 inch to little more than three inches in 

 length. Most of them are found along- 

 sandy shores and are prone to burj^ almost 

 the entire ' body in the sand, leaving only 

 the mouth with the expanded buccal cirri 

 protruding' (p. 9). Nevertheless one 

 specimen was described in 1889 in the ' Re- 

 port on the pelagic fishes ' of the Challenger 

 Expedition (p. 43), and affirmed to have 

 been taken ' a few degrees north of Hono- 

 lulu,' from 'a deep haul 1,000 fathoms ' of an 

 open-mouthed dredge. 



Diverse are the views that have been 

 held respecting the affinities of the Lance- 

 lets. From a single small specimen obtain- 

 ed on the Cornish coast, Pallas in seven 

 lines described the species in 1774* (not 

 1778, as Mr. Willey states) and called it 

 lAmax laneeolatus or lanceolaris. Under the 



*Spicilegia Zoologica [etc.]. Fasciculus decimus. 

 Berolini [etc.], 1774. (p. 19, pi. 1., fig. 2.) 



name Limax, Pallas included naked gastro- 

 pods, whether broad or narrow, having a flat 

 foot, and he mistook the metapleural folds 

 and intermediate area of the new species 

 for a foot. No further notice was taken of 

 the species till 1834, when Costa described 

 it anew as BrancMostoma hibricitm, and in 

 1836 Yarrell redescribed it. and, with the ^1 

 assistance of John Edward Gray, identified 

 it with the long-neglected Limax of Pallas 

 and called it Am2Moxtis laneeolatus. 



Both Costa and Yarrell thought that it ^ 

 belonged with the Lampreys aad Hags. J. j 



Miiller first recognized how important were 1 



its peculiarities and in 1844 gave it subclass j 

 rank. Isidore Geofifroy St. Hilaire in 1852 

 and C. Bonaparte in 1856 first elevated it 

 to class rank. Haeckel in 1866 advanced 

 still further and contrasted the class of lan- 

 celets as a subphjdum (Acrania) M-ith all 

 the other vertebrates (Craniota). This last 

 view is adopted by Mr. Willey who how- 

 ever prefers the later name, Cephalochorda, 

 for the 'division.' The familj^ name, 

 Branchiostomidce, Avas first given bj' Bona- 

 parte in 1846. 



With so much interest attached to thetn, 

 the lancelets naturallj' have received much 

 attention, and manj^ elaborate memoirs on 

 various parts of their structure have been 

 published. Of the 140 (133 + 7) titles re- 

 corded by Mr. Willej' in his bibliographical 

 'references' (pp. 295 — 309), 66 are under 

 the head ' Anatomj' of Amphioxus,' and 37 

 under the caption ' Development of Am- 

 phioxus.' Mr. Willej' very properly adds 

 that "this bibliographj' does not by any 

 means include all that has been written on 

 the anatomy of Amphioxus." Indeed, the 

 titles could be more than doubled, but with- 

 out material advantage to the value of the 

 work for most readers. Eeally Mr. Willey 

 has prepared a very useful and well made 

 list and mainlj' with well considered restric- 

 tions. In view of such an abundant litera- 

 ture the need for a general work embodying 



