198 MICHIGAN ACADEMY OF SCIENCE. 



length of the arms, character of the pinnules, and the color are matters 

 which depend to a large extent on the age of the individual, so that 

 there might be a marked diftoronce in all these points, which would be 

 only a difference of years and not of species. 



Taking these facts into consideration it has seemed best to call these 

 specimens Mctacrinus rotundus, as that was the first of the three species 

 to be described. The fact that the ''Vega" specimen has never been writ- 

 ten up makes it impossible to reach any definite conclusion about its 

 relation to rotundus and interruptiis, but from the facts in hand it 

 would seem that there are no essential differences in the structure of 

 these three individuals to warrant this differentiation into species. 



To turn now to a few observations on the reproductive organs of 

 Metacrinus. The reproductive organs of the crinoids consist of five 

 genital strands, arising in the upper part of the calyx from the spongy 

 organ, which is the termination of the axial organ, running into each of 

 the five rays, branching with them and entering the last ramifications, 

 the pinnules. This genital strand commonly known as the rachis, lies 

 normally in a small sinus between the three branches of the body cavity 

 and as a rule remain;-' infertile in the arms. Generally the genital 

 strand is at first solid, widening only in the pinnules into a hollow 

 genital tube, from the ei)ithelium of which arise either ova or spermatozoa. 

 There are, however, occasional exceptions to this rule, as the following 

 quotation from Carpenter's ve))ort will show: ''In some sections that 

 were cut for Sir Wyville Thomson by Br. Stirling the ovary appears 

 in the arm, occupying the usual viosition between the sub- tentacular and 

 the coeliac canals, where the sterile genital chord is normally found. 

 This is also the case in the lower parts of the arms of Holopus but I have 

 not yet succeeded in discovering which species of Metacrinus or Penta- 

 crinus is distinguished by this peculiarity; for the sections above men- 

 tioned were not labelled with any name or reference number. I have cut 

 sections of all the more common Pentacrinidae, but in none of them 

 have I found any such depailure from the type of the ordinary Antedou as 

 is presented by the ovaries of this unknown species." On cutting cross sec- 

 tions from the arm of rotundus I found this peculiarity which Carpenter 

 here mentions, a well developed, functional ovary in the palmars, lying 

 between the three branches of the body cavity and occupying a large 

 part of the ventral side of the arm. The genital rachis remains distinct 

 nearly all the way, merging in but one spot into the ovary and soon re- 

 appearing to give off a branch to the succeeding pinnule. The branches 

 running into the pinnules are much larger than the main strand and as 

 they start some little distance below the base of the pinnule in the arm 

 itself, might easily be mistaken for the rachis. They do not appear to be 

 functional however, and a careful investigation of a number of indi- 

 viduals revealed nothing in the way of an ovarian pinnule, so common 

 in other crinoids. There appear to be no definite genital openings from 

 the ovary and it is probable in this case, as in all others, that the ova 

 escape by a rupture of the body wall. Further sections through the 

 calyx of another individual revealed a small ovary lying in the body 

 cavity, surrounded by loose connective tissue. This is not an unknown 

 departure from the ordinary manner of reproduction for Carpenter found 

 such ovaries in two species of Antedon and one Actinometra. 



The fact that in rotundus the number of radials is rather variable, 



