Nov. 



:888] 



NATURE 



21 



. :.L gill-arches. Black pigment is present in the anterior part of 

 its inner portion. 



Epithelium. — The epithelium lining the mouth consists of 



polygonal cells, apparently without cilia. In the pharyn.x, nests 



of simple glands, like those of the tongue, are present ; and, as 



already mentioned, numerous sense-organs are to be found in 



•'f region of the gill-clefts. The epithelial cells of the stomach 



i intestine are columnar, but vary much in their form and 



portions. Cilia could be detected here and there ; in ajl 



l)ability they occur in isolated regions, as in the adult 



iprey. 



With the exception of the large liver, there is no trace of any 

 ad in connection with the stomach and intestine, and diges- 

 n must be thus performed largely through the instrumentality 

 leucocytes. 



Mtisclc-s of I he Alimentary Canal. — The muscles of the walls 

 <if t)0tli stomach and intestine are only very slightly developed 

 in torpid specimens, and are apparently broken up and separated 

 by the lymphatic tissue to be described presently. They probably, 

 therefore, undergo a similar degeneration to that observed in the 

 caudal muscles. 



Lymphatic Otgans of the Stomach and Intestine. — The form of 

 these organs has been described by Ayers {loc. cit.) I have not 

 been able to verify his supposition that there are direct connec- 

 tions between them and the lumen of the intestine. A central 

 part of the lymphatic orgran running down the axis of the spiral 

 valve can be distinguished from the rest by its more compact 

 structure. Many of the leucocytes in these regions are full of 

 fat-globules. 



A large lymphatic body is present behind the cloaca and 

 pelvis, and probably serves to proteqt the vent from the entrance 

 of harmful substances. 



Cloaca! Cacum. — The so-called "urinary bladder" opens 

 into the cloaca between the rectum and the urinary and genera- 

 tive ducts. It has therefore much the position of the "rectal 

 gland " of Selachians, and probably has nothing to do with the 

 urinar)- bladder of other forms. 



Lungs. — The cavity of the lungs is divided up by trabeculae, 

 which give the anterior unpaired portion a sponge-like appear- 

 ance : a central lumen is present in the paired portion, A large 

 lymphatic organ lies beneath the anterior unpaired part, the 

 curious relations of which I hope to describe later, and will now 

 only mention that the blood corpuscles migrate from it into the 

 tissues of the lung. 



Abdominal Pores. — As Ayers has shown, only one abdominal 

 l>ore is usually present, and in my sections this ends blindly, 

 and does not open into the ccelome. Probably its relations vary 

 in different individuals. 



Blood Corpuscles.— Ti\Q chief peculiarity of the blood of 

 Protopterus is the large size of the corpuscles, and the compara- 

 tively large proportion of the white in comparison with the red. 

 The form of the latter resembles that of the red corpuscles of Arn- 

 phibians. In length they measure from o'040-o"046 mm., and in 

 width o 025-0 027 mm. The size of the white corpuscles varies 

 greatly. The diameter of the largest, when not throwing out 

 pseudopodia, may exceed the length of a red corpuscle. Two 

 kinds maybe distinguished, as follows :—(l) Large leucocytes 

 of the ordinary form, the protoplasm of which is usually dis- 

 tinctly differentiated into a coarsely granular endoplasm and a 

 hyaline ectoplasm. In specimens prepared for me by Dr, 

 Goldmann, according to Dr. Ehrlich's method, the protoplasm 

 :ind nucleus are coloured violet. (2) Leucocytes of various 

 Vizes, the largest being usually rather smaller than those described 

 iliove. The granules in the protoplasm are finer, and in addition 

 . the ordinary blunt pseudopodia, stiff filamentous processes are 

 o formed. The protoplasm of these stains brownish-red by 

 i.hrlich's method, and Dr. Goldmann informs me that a similar 

 coloration occurs in human white corpuscles in cases of 

 leukemia. Prof. August Gruber was kind enough to make 

 ^ careful examination of these corpuscles with me, and we were 

 le to trace a gradual disintegration in those described under 

 -), until finally nothing but the greatly altered nucleus is left, 

 it seems probable, therefore, that these leucocytes convey the 

 nutriment from the alimentary canal (or muscles) into the blood, 

 ■and there disintegrate. 



lUood-vessels. — I have at present only one or two remarks to 



iike on the arrangement of the blood-vessels. Hyrtl's descrip- 



'^n ' of the vessels of Lepidosiren would answer equally well in 



snost points to Protopterus. Peters - describes a single pulmonary 



' AbhanJlungen d. bdhm. GescU. d. Wiis., 1845. 



=> Mull. Arch./. Anat., i345- 



artery, arising from the efferent branchial vessels on the left 

 side. This soon branches into two, each branch running along 

 the inner side of the corresponding lung. No mention, however, 

 is made by Peters of the corresponding right vessel, which has 

 precisely the arrangement described by Hyrtl in Lepidosiren, 

 This right pulmonary artery also divides into two, one branch 

 passing along the dorsal surface of each lung alongside the pul- 

 monary branch of the vagus. 



The caudal vein divides up into two renal-portals. These 

 are said by Hyrtl to anastomose anteriorly with a paired azygos 

 in Lepidosiren. I have been unable to find any such "azygos 

 vein" in Protopterus. The two so-called "vence cavc-e pos- 

 teriores " doubtless correspond to the posterior cardinals, though 

 they are somewhat modified. No lymphatic vessels could be 

 detected. 



Urinary Organs.— The kidneys are closely invested every- 

 where except on their dorsal side, by lymphoid and fatty tissue, 

 which posteriorly forms a large median mass, plugging the end of 

 the ccelome. No nephrostomes are present, as was supposed by 

 Ayers. 



A quantity of pigmented tissue on the outer and lower borders 

 of the kidneys may possibly represent the adrenals. 



Generative Organs.— Concerning the structure of the female 

 generative organs, I have, as yet, little to add to the descriptions 

 of former observers. No accurate account of the male organs 

 exists, and I am inclined to think that the descriptions which 

 have been given up to the present time referred to immature 

 females, the generative organs of which might easily be taken for 

 those of a male. 



I have been able to distinguish no essential differences in 

 external form between males and females : the latter are by far 

 the more abundant. 



Each testis has much the form and relations of an immature 

 ovary, and, like the ovary, is invested along its free edge and 

 sides with lymphatic and fatty tissue. Along its ventral surface 

 a slight groove can be distinguished, at the bottom of which the 

 spermatic duct lies. Posteriorly, the two ducts come to the 

 surface, unite, and open by a common aperture on a papilla into 

 i the cloaca, just as in the female. In transverse sections, the 

 j seminiferous tubules can be seen opening into the ducts ; in 

 I ripe specimens, fully formed spermatozoa can be seen in their 

 lumina. I have, up to the present time, found nothing which 

 1 could correspond to the remnant of a Miillerian duct, and, as 

 the ureter undoubtedly must represent the mesonephric duct, 

 I there remains no other explanation of the duct of the testis than 

 j to suppose it to be the homologue of the Miillerian duct. 

 j The form of the spermatozoa is very curiou=; : they are carrot- 

 shaped, and each is provided with two long cilia. They are 

 , very small, the length of the carrot-shaped head being only 

 ' about 1/25 mm. 



Most of the above observations were made in the Ana- 

 tomical Institute in Freiburg i/B, where I have profited much 

 by the kind help and advice of Prof. Wiedersheim. 

 August 31, 1888. W. Newton Parker. 



A more detailed examination of a male specimen, m which 

 the spermatozoa were not yet ripe, has shown that distinct rudi- 

 ments of the anterior parts of the Mullerian ducts are present. 

 Each has an abdominal aperture, similar in form and position 

 to that of the oviduct, and extends backwards for a short dis- 

 tance, tapering off before the level of the kidneys is reached. 

 In sexually mature individuals, all traces of the Mullerian ducts 

 appear to have vanished. 



The duct of the kidney must therefore, as in Elasmobranchs, 

 represent a special collecting-tube developed in connection with 

 the posterior mesonephric tubules. W. N, P. 



University College, Cardiff, October 27. 



THE WHEAT CROP OF 1888. 



SIR JOHN LAWES has communicated some interesting facts 

 with regard to the wheat crop of the present year. It has 

 been Sir John Lawes's endeavour for many years past to establish 

 a statistical relation between the fluctuations of the yield of wheat 

 upon his own well-known experimental field in Hertfordshire 

 with the general average obtained over the United Kingdom. In 

 order to do this he has selected certain plots and taken their 

 average yields, and it is maintained that the result so obtained 

 fairly represents the average yield over the United Kingdom. 



