ON TlIK l)i:\ E1.«)L'MK.N'J' < )F LLMtJLUS LOMilSPIXA. 59 



ventral plate (figs. 8, 9. mar. hd.). Packard'' describes the band accu-. 

 rately. He sa^^s : " Around the edge (of the ' primitive disk ') is a pale 

 areola, destined to 1)e tlie lower edge of the carapace ; it is most distinct 

 along the middle, merging imperceptibly into the anierior and posterior 

 piid of the disk, tt is a thin ridge, due to a local heaping up of cells."' 

 Almost simultaneously wirb tlie appenrance of tlie Tiiai-ginal bands, two 

 ]»:ii]'ed longitudinal grooves ore formed jnst internal to the band and 

 parallel with the median line of the ventral plate. 1 shall call the 

 outer of these longitudinal grooves the first, and the inner of them, the 

 second, lateral longitudinal groove (figs. 8 ik 9, 1 lat. gr., 2 Jat. (jr.). 

 The first appendage-bearing segmeiit had become cut ofi' ïvom the 

 cephalic lobe. /./'., the fir-t segment of the earlier stages (fig>. 4 Ä 7) 

 had thus been di\ ided into tlie first appendage-bearing segment and 

 tlie cephalic lobe. The cephahc lobe which was earlier clearlv divided 

 into two lateral halves had now begun gradually to unite (fig. 8), and 

 in fig. 9 is seen completely united, no dark line being found in tlie 

 median part of it. The sixth appendage-bearing segment had become 

 cut off. Tbe median line had heeM mucli produced and almost 

 reached the posterior end of tlie ventral plate. fhe posterior part 

 of the line is grooved. 



On August 14th (17 days after spawning), the stomodaeum (^st.) 

 was distinctly seen in the cephalic lobe, at the anterior end of the Ion o-i- 

 tutlinal median h'ne (fig. 10). It is a very shallow, roundish de]»r('s- 

 sion. liudiments of the distal end of the appendages had now become 

 distinct as round protuberances witliin the marginal IvumI and were 

 very conspicaious feafiu-es of the ventral pla(<^ In the marginal band 

 and external to the fourth a])pendage; paired, round protuberances (/a/. 

 li.) appear. They are a litrle larger than tlie rudiments of appendages. 

 As the function as well ;is homology of these peculiar protuberances 



2) Packard — The Development of Limulu!: pohjphemus. Mem. Bost. Soc. Nat. Hist. vol. II. 



