132 DR A. MILNES MARSHALL ON THE 



The anatomy of the polyp, so far as I have had the chance of investigating 

 it, agrees with that of other Virgularia?. The reproductive organs, as in 

 Virgularia? generally, are contained, not in the mature polyps, but in the im- 

 mature ones at the lower end of the rachis. 



The large specimen (fig. 1) is a male, and a small part of the rachis removed 

 from a point 22 mm. from the lower end of the stalk, showed the mature male 

 organs or spermatospheres. These (fig. 3) have the typical structure of the 

 male organs of Pennatulids. They are oval or spherical bodies, the largest of 

 which have a diameter of 0*38 mm." Each is enclosed in a very thin capsule, the 

 contents of which are a mass of very minute brightly refracting bodies — the 

 heads of the spermatozoa ; these are more closely packed at the periphery than 

 in the centre, where a number of fine radiating filaments can be seen, which are 

 probably the spermatozoa tails. 



The smaller specimen, in which the lower end of the rachis is present, was 

 also -examined for reproductive organs, but none were found. The third 

 specimen, consisting of the middle part alone of the rachis, is of course devoid 

 of reproductive organs. 



This specialisation of the reproductive organs to the immature polyps is 

 undoubtedly a sign of considerable differentiation, and marks Virgularia as a 

 less primitive genus than such a form as Pennatula. For while in the latter 

 the component individuals of the colony are of two kinds only — zooids and 

 polyps — in Virgularia they are of three kinds — zooids, nutrient individuals, and 

 reproductive individuals. Whether all the immature polyps ultimately develop 

 into mature ones is uncertain ; probably not, inasmuch as all recorded specimens 

 of Virgularia have immature polyps at the lower end of the rachis. The 

 abrupt transition from the immature to the mature polyps described above as 

 occurring in the second example of V. tuberculata, may perhaps indicate the 

 existence of a sharp line of demarcation between the sexual and the nutrient 

 individuals. 



Whether zooids are present or not in V. tuberculata, I have been unable to 

 determine with certainty without destroying the specimens. Certain very small 

 knob-like projections on the rachis near the base of the polyps may perhaps 

 prove to be zooids ; if so, they are in an exceedingly rudimentary condition. 



As noticed above, all three specimens of V. tuberculata are imperfect, and 

 their imperfection is of some interest, inasmuch as it is very characteristic of 

 dredged specimens of Virgularia generally. Of the type species, V. mirabilis, a 

 perfect specimen has never yet been seen, all the specimens recorded being 

 fractured either at one or both ends. The lower ends or stalks are occasionally 

 found perfect, but the upper end never, the only known exception being a 

 single specimen in the Glasgow Museum. 



The cause of this mutilation has been elsewhere discussed. It has been 



