Macalister — 071 tico Nno Species of Pentastoma. Qo 



ing to a fine point ; by these organs the spermatozoa are conveyed 

 upward on their long journey to the spermaphores of the female. 



As anterior diverticula from these are two lateral thick- walled sacs 

 each lined with a ridged and processed chitinous membrane. These 

 accessory sacs are hollow, and their chambers communicate with each 

 other by a transverse, anterior, annular canal over the oesophagus. 

 The use of these sacs is unknown. These cirrus pouches and their 

 accessory parts are much larger than in P. tcenioides, where these organs 

 are small and limited to lateral areas beside the chitin sac-organs. 



The ova were found in several stages of development in some of the 

 females, from the perfectly undeveloped egg with germ-spot and 

 vesicle to the bi or multipartite cleft yelk of the fertilized egg. In 

 some of the latter the spherules were very disproportionate in size, 

 some six times the size of the others, and the larger always had a ten- 

 dency to one side or surface of the ovum. The eggs are holoblastic, 

 and segmentation ends in the formation of a blastoderm. There are 

 polar groups of cells visible in some ova and a trace of primitive streak, 

 subdividing the tail end of the egg into two lateral parts. "When the 

 body forms as a granular mass six lateral lobules project downwards 

 and outwards, two of which unite to form the basis of the antennary 

 jaws of the head, two form the larval forelimbs, and the hindmost pair 

 form the hind legs. The first and second pair of these form first, the 

 hindmost afterwards. In several of the hundreds of ova which I 

 examined I saw a faint trace of annulation, one or two transverse fur- 

 rows, indication of a metameric growth. In one embryo which is 

 obliquely shown (Plate 3, fig. 11) these are indicated (and rather exag- 

 gerated), and two of the limbs are shown, armed with paired claws. In 

 the earlier stages before the claws appear the knobs look like the para- 

 podia of worms, but a middle transverse joint in each of these limb 

 knobs is indicated in some of my specimens. Two free embryos fur- 

 ther developed than any of those enclosed in the egg membranes are 

 shown Plate, figs. 12 and 13. In these the larval form is easily recognis- 

 able. In no stage nor specimen did I see a trace of the simple salivary 

 gland which exists- in P. tcenioides. 



The adult hooks are not the descendants of the embryonic limbs, 

 but seem to indicate segments anterior to the three limb-bearing 

 segments of the larva. The extremely complex subsequent-develop- 

 mental stages I had no means of investigating. 



In the above observations I have refrained from quoting from the 

 classical memoir of Leuckart on the Pentastomidas, our chief source 

 of infurmation on these aberrant arthropods, as I Avish to make this 

 Paper only a record of direct observation. 



"We may summarize the specific characters of this species thus : 

 Pentastoma imperaioris, body with 40-45 rings, clearly annulated 

 behind, more indistinctly in front ; head acutely wedge-shaped with 

 no lateral stigmata, but with several median dorsal warts ; hooks 

 simple with slender basal processes ; vulva very close to the vent ; pos- 

 terior end dilated pyriform, with its narrowest end terminal ; stomach 



E, I, A. PROC, SEE. II. VOL. II., SCIENCE. K 



