10 



Mespilia (jlubiilus, \*\. \ II l"ii>s. 1 and 2, onv boin.^ drawn from a living 

 specimen, Ihe oilier from an especially carefully preserved specimen, 

 give a striking example of I his. (The Asteroid and Holothurioid larva>, 

 which have no suppoiliiiij ski-lclon, are much easier to |)reservc in good 

 shape). liul Ihcn, worst of all, in many cases the sfcelelon was found lo 

 have been dissolved. The slightest trace of acidity will resull in destroy- 

 ing such fine calcareous structures: although I used always Ihc jjurest 

 alcohol obtainable for the preservation of these larvte, the result proved 

 fatal in only too many cases. Traces of the skeleton are still recognizable 

 in many cases and the dissolution has generally proceeded so slowly that 

 the organic matrix of the calcareous substance may still show the shape 

 of the skeleton almost undisturbed; but for the purpose of studying the 

 morphology of the skeleton and its specific characters in the dilTerenl 

 larval forms it is of no use. liven the preservation in Canada balsam does 

 not give safe guarantee against the dissolution of the skeleton; in some of 

 these larva^ also their skeleton has disappeared more or less comj)lctely. 

 The matter is not simply explained by staling thai Ihe alcohol or the 

 balsam nmst have been acid, ft may happen that while some specimens 

 have had the skeleton dissolved, others preserved in the same lluid and 

 lying side by side with them in the same jar have the skeleton well preserv- 

 ed; in the same way, of larvae imbedded in Canada balsam from one and 

 the same tube and at the same time some may have the skeleton preserved, 

 while in others it is completely dissolved. - Whatever now the explana- 

 tion may be, this dissolution of the larval skeleton has in several cases 

 considerably deteriorated the value of my researches — especially nuieh 

 of the work done on Hawaii was spoilt thereby. 



Besides the morphology of the larva' attention has also been paid lo 

 the question about their dislribulion over the ocean. Already during the 

 author's voyage to Siam in 18'.)9 — 1*.)UU opportunities were taken to collect 

 plankton samples on the passage across the Indian Ocean, and again on 

 the passage out to the F^ast across the Indian Ocean plankton was collected 

 daily, by means of the wash-deck pump, the water from it being sifted 

 through a usual plankton net. Although somewhat deteriorated by rust 

 such plard<ton samples could be very well utilized and gave very valuable 

 infonnation about the occurrence of Mchinoderm larva? in the open sea. 



In the years 1910 lUl!) |)lanklon .samples were collected for me on 

 board the Danish cruiser Tngolf" on its cruises lo the West Indies by the 

 young naturalists 11. Blegvad, 1*. Kranip and 11. Fogh. In this way 

 six series of samples were collected across the Atlantic, which have resulted 

 in important information of the distribution of Echinoderm larvae over 

 this ocean - as also in the finding of several interesting larval types. In 



