142 0. HRRP.RRT FOWLER. 



EXPLANATION OF PLATES 11 and 12, 



Illustrating Dv. G. H. Fowler's paper on " Planktonetta 

 atlantica, Borgert." 



All tlie figures have been drawn with the Abbe camera. 



In rigs. 1 — 3 the spines of the arms liave been omitted. 



Pig. 1. — View approximately from the right side and somewhat anteriorly, 

 the left pair of arms omitted. Below is the shell, containing the central 

 capsule ; into the latter projects the dark intra-capsular protoplasm, slightly 

 trefoil-shaped, with two fainter wings, probably produced by the vacuolated 

 protoplasm (cf. Fig. 9). The shell is narrowest just above this region, and 

 expands at the mouth, which is largely covered by the dark granular phseodial 

 or extra-capsular protoplasm and corpuscles. The float lies posteriorly. 

 X 6-6. 



Fig. 2.— From the oral aspect, looking down on the phseodium ; behind 

 this the outline of the shell body. The float is clearly seen to lie posteriorly. 

 X 6G. 



Fig. 3. — View aborally and slightly anteriorly, the anterior prominence of 

 the shell body towards the observer, x G'6. 



Fig. 4. — Small portion of the mouth of the shell from the outside, showing 

 the zone of polygons at the lip, the middle smooth zone with pores, the lower 

 pitted zone passing into the homogeneous shell, two of the spines of which 

 are also represented, x 140. 



Fig. 5. — Mouth of the shell viewed from the posterior aspect, showing the 

 origin of the arms, all spines and the polygonoid structure omitted, x 32. 



Fig. 6. — Mouth of the sliell from above (orally) looking down into the 

 circular aperture, only some of the long spines (sp. i) remaining, x 48. 



Fig. 7. — (t- Low-power view of about two thirds of an arm, the spines 

 broken, x 3G. b. Termination of an arm, showing the two layers of which 

 it is composed, and the laniinse which cross its lumen. One lateral spine showing 

 dichotomous branching into sixteen has been drawn ; for the terminal whorls 

 of hooks the reader is referred to Dr. Borgert's paper. Of the three terminal 

 branches of the arm only one has been drawn, with three tines ; the cavity of 

 the end branches is not continuous with the general lumen of the tul)e. 

 X 140. 



Fig. 8. — Part of an antero- posterior section to siiow the topographical 

 relations of the dia|)hragm (d.), its free edge (d. i), the thicker lower (c. c. i) 

 and thinner upper [e.c.'\\) parlsof the central capsule, as actually presented 

 in sections, x 90. 



